* The unnamed buffer is also used for reading from --stdin, so you couldn't practically combine
  --stdin with passing command-line arguments to macros.
* The old approach of passing command-line arguments via lines in the
  unnamed buffer was flawed anyway as it wouldn't work with filenames containing LF.
  This is just a very ancient feature, written when there weren't even long Q-reg names in SciTECO.
* You can now e.g. pipe into SciTECO and edit what was read interactively, e.g. `dmesg | sciteco -i`.
  You can practically use SciTECO as a pager.
* htbl.tes is now a command-line filter (uses -qio).
* grosciteco.tes reads Troff intermediate code from stdin, so we no longer need
  "*.intermediate" temporary files.
* added a getopt.tes test case to the testsuite.
* This change unfortunately breaks most macros accepting command-line arguments,
  even if they used getopt.tes.
  It also requires updating ~/.teco_ini - see fallback.teco_ini.

* Improves DEC TECO-11 compatibility.
* <EM> is still supported as a synonym, but considered deprecated and is no longer documented.
  A warning is printed when invoked.
  It can be repurposed at any time in the future.
* `EI$` is not yet supported.
  I am unsure whether this makes any sense.

* All commands and their documentations were inconsistent.
  * ^W rubbed out to the beginning of words.
  * Shift+Right (fnkeys.tes) moved to the beginning of the next word if
    invoked at the beginning of a word and to the end of the next word otherwise.
  * <W> (and <V> and <Y> by extension) moved to the end of the next word.
  * The cheat sheet would claim that <W> moves to the beginning of the next word.
* Video TECO's <W> command would differ again from everything else.
  With positive arguments, it moved to the beginning of words, while
  with negative it moved to end of words.
  I decided not to copy this behavior.
* It has been decided to adopt a consistent beginning-of-words policy.
  -W therefore differs from Video TECO in moving to the beginning of the
  current or previous word.
* teco_find_words() is now based on parsing the document pointer, instead
  of relying on SCI_WORDENDPOSITION, since the latter cannot actually be
  used to skip strictly non-word characters.
  This requires a constant amount of Scintilla messages but will require fewer
  messages only when moving for more than 3 words.
* The semantics of <W> are therefore now consistent with Vim and Emacs as well.
* Shift+Right/Left is still based on SCI_WORDENDPOSITION, so it's behavior
  differs slightly from <W> for instance at the end of lines, as it will
  stop at linebreaks.
* Unfortunately, these changes will break lots of macros, among others
  the M#rf, M#sp and git.blame macros ("Useful macros" from the wiki).

* significantly speeds up build time
* Scintilla and Lexilla headers and symbols are all-ASCII anyway.
* We should probably have a look at the quicksort implementation
  in string.tes, as it can probably be optimized in UTF-8 documents as well.

* There is cleanup that is not strictly necessary, because it only frees memory
  which is freed on program termination anyway.
* However, it helps to explicitly free everything for debugging memory leaks via Valgrind.
* The new macro reduces the number of #ifdef statements.
* On NDEBUG, the code of these functions will still be eliminated.
* If functions are referenced only from the destructor, there will be no unused function
  warnings, even in NDEBUG.

* when hosted on Windows, the default is DOS linebreaks
* Unix linebreaks are in many cases more consistent as all other sources use Unix linebreaks
* woman pages with Unix linebreaks are slightly faster to load due to EOL conversion
* especially Groff input must not contain CR as it will otherwise log lots of warnings
  (affects htbl.tes and tedoc.tes).

* There is a "Scintilla.h" as well.
* should fix macOS and builds on native Windows hosts
* It wasn't practical to refer to the Scintilla includes using paths since
  the Scintilla location is configurable (--with-scintilla).
  So we'd have to write something like #include <include/Scintilla.h>.
  For Scinterm we cannot avoid collisions neither as its path is also
  configurable (--with-scinterm).
  Effectively, we must prevent name clashes across SciTECO and all
  of Scintilla and Scinterm.

This is a total conversion of SciTECO to plain C (GNU C11).
The chance was taken to improve a lot of internal datastructures,
fix fundamental bugs and lay the foundations of future features.
The GTK user interface is now in an useable state!
All changes have been squashed together.

The language itself has almost not changed at all, except for:

* Detection of string terminators (usually Escape) now takes
  the string building characters into account.
  A string is only terminated outside of string building characters.
  In other words, you can now for instance write
  I^EQ[Hello$world]$
  This removes one of the last bits of shellisms which is out of
  place in SciTECO where no tokenization/lexing is performed.
  Consequently, the current termination character can also be
  escaped using ^Q/^R.
  This is used by auto completions to make sure that strings
  are inserted verbatim and without unwanted sideeffects.
* All strings can now safely contain null-characters
  (see also: 8-bit cleanliness).
  The null-character itself (^@) is not (yet) a valid SciTECO
  command, though.

An incomplete list of changes:

* We got rid of the BSD headers for RB trees and lists/queues.
  The problem with them was that they used a form of metaprogramming
  only to gain a bit of type safety. It also resulted in less
  readble code. This was a C++ desease.
  The new code avoids metaprogramming only to gain type safety.
  The BSD tree.h has been replaced by rb3ptr by Jens Stimpfle
  (https://github.com/jstimpfle/rb3ptr).
  This implementation is also more memory efficient than BSD's.
  The BSD list.h and queue.h has been replaced with a custom
  src/list.h.
* Fixed crashes, performance issues and compatibility issues with
  the Gtk 3 User Interface.
  It is now more or less ready for general use.
  The GDK lock is no longer used to avoid using deprecated functions.
  On the downside, the new implementation (driving the Gtk event loop
  stepwise) is even slower than the old one.
  A few glitches remain (see TODO), but it is hoped that they will
  be resolved by the Scintilla update which will be performed soon.
* A lot of program units have been split up, so they are shorter
  and easier to maintain: core-commands.c, qreg-commands.c,
  goto-commands.c, file-utils.h.
* Parser states are simply structs of callbacks now.
  They still use a kind of polymorphy using a preprocessor trick.
  TECO_DEFINE_STATE() takes an initializer list that will be
  merged with the default list of field initializers.
  To "subclass" states, you can simply define new macros that add
  initializers to existing macros.
* Parsers no longer have a "transitions" table but the input_cb()
  may use switch-case statements.
  There are also teco_machine_main_transition_t now which can
  be used to implement simple transitions. Additionally, you
  can specify functions to execute during transitions.
  This largely avoids long switch-case-statements.
* Parsers are embeddable/reusable now, at least in parse-only mode.
  This does not currently bring any advantages but may later
  be used to write a Scintilla lexer for TECO syntax highlighting.
  Once parsers are fully embeddable, it will also be possible
  to run TECO macros in a kind of coroutine which would allow
  them to process string arguments in real time.
* undo.[ch] still uses metaprogramming extensively but via
  the C preprocessor of course. On the downside, most undo
  token generators must be initiated explicitly (theoretically
  we could have used embedded functions / trampolines to
  instantiate automatically but this has turned out to be
  dangereous).
  There is a TECO_DEFINE_UNDO_CALL() to generate closures for
  arbitrary functions now (ie. to call an arbitrary function
  at undo-time). This simplified a lot of code and is much
  shorter than manually pushing undo tokens in many cases.
* Instead of the ridiculous C++ Curiously Recurring Template
  Pattern to achieve static polymorphy for user interface
  implementations, we now simply declare all functions to
  implement in interface.h and link in the implementations.
  This is possible since we no longer hace to define
  interface subclasses (all state is static variables in
  the interface's *.c files).
* Headers are now significantly shorter than in C++ since
  we can often hide more of our "class" implementations.
* Memory counting is based on dlmalloc for most platforms now.
  Unfortunately, there is no malloc implementation that
  provides an efficient constant-time memory counter that
  is guaranteed to decrease when freeing memory.
  But since we use a defined malloc implementation now,
  malloc_usable_size() can be used safely for tracking memory use.
  malloc() replacement is very tricky on Windows, so we
  use a poll thread on Windows. This can also be enabled
  on other supported platforms using --disable-malloc-replacement.
  All in all, I'm still not pleased with the state of memory
  limiting. It is a mess.
* Error handling uses GError now. This has the advantage that
  the GError codes can be reused once we support error catching
  in the SciTECO language.
* Added a few more test suite cases.
* Haiku is no longer supported as builds are instable and
  I did not manage to debug them - quite possibly Haiku bugs
  were responsible.
* Glib v2.44 or later are now required.
  The GTK UI requires Gtk+ v3.12 or later now.
  The GtkFlowBox fallback and sciteco-wrapper workaround are
  no longer required.
* We now extensively use the GCC/Clang-specific g_auto
  feature (automatic deallocations when leaving the current
  code block).
* Updated copyright to 2021.
  SciTECO has been in continuous development, even though there
  have been no commits since 2018.
* Since these changes are so significant, the target release has
  been set to v2.0.
  It is planned that beginning with v3.0, the language will be
  kept stable.

 * Fixed build problems on Windows
 * g_slice on Windows has been shown to be of little use either
   and it does not work well with the GetProcessMemoryInfo()
   measurements.
   Also, it brings the same problem as on Glibc: Not even command-line
   termination returns the memory to the OS.
   Therefore, we don't use g_slice at all and commented on it.
 * The custom Linux and Windows memory measurement approaches
   have been shown to be inefficient.
   As a workaround, scripts disable memory limiting.
 * A better approach -- but it will only work on Glibc -- might
   be to hook into malloc(), realloc() and free() globally
   and use the malloc_usable_size() of a heap object for
   memory measurements. This will be relatively precise and cheap.
 * We still need the "Object" base class in order to measure
   memory usage as a fallback approach.

 * this uses an optstring compatible with getopt(3).
 * It does not use repeated getopt calls to iterate options, though
   but places the results in registers beginning with "getopt.".
   E.g. option "C" will result in "getopt.C" being set after the
   call to setopt.
   String arguments are supported and are placed in the string part
   of the getopt registers.
 * The grosciteco.tes and symbols-extract.tes scripts make use of
   getopt now, to simplify and clean up their command line handling.