* This mirrors how the `FT$` command toggles through several results.
* Some non-unique .SCITECO_TOPICs have been added to sciteco(1) and sciteco(7).
* This works by inserting non-unique keys into the help topic RB tree - or rather
  by turning filename:pos also into keys since rb3ptr does not allow non-unique keys.
  When searching for a topic, we sort lower than any other entry with the same name.
  This way we can easily iterate all entries with the same name (search topic).
  The alternative would have been to maintain a linked list in each and every
  teco_help_topic_t.
* teco_rb3str_auto_complete() now filters out possible duplicate keys.
* Updated test case: check for non-unique topic names.

This currently only works in insert commands after enabling the immediate
editing modifier via CTRL+G and if the LSP was already launched
(e.g. by an explicit `FT$`).
File name completions are still performed with an activated ^G modifier
only if the LSP is shut down.

Just like for file names, the modifier is automatically cancelled after
a successful completion - there is little sense in completing several
symbols in a row.

This will be important once we're doing LSP auto-completions.
Until a completion is complete, we do NOT want to disable the modifier however
since otherwise it can be disabled after a partial completion if there happened
to be a rubbed out command line.
Discarding a rubbed out command line consequently no longer disables
the modifier as well.

Any change of the modifier is now logged with an Info-level message.

Some rudimentary test case has been added for rub-in via ^G.

This is similar to `\` at the line end in many languages like C and
allows you to split a very long string argument over several lines without
adding the EOL characters themselves.
The TECO equivalent to `\` would be ^Q, but it would be a semantic exception since
^Q (escaping) is supposed to _preserve_ the value of the following character.
Therefore I decided to use ^E instead.
This works with DOS and Mac line breaks as well.

If you have projects in different languages you can set different LSPs.
The default will still come from ~/.teco_ini if you decide to set one.
The default for $SCITECO_LSP_ROOT is set by session.tes' VCS integration
based on the VCS root, but you could still overwrite it per session.

* The main interface is the `FT` command.
  `FT` was an undocumented Video TECO command for etags/ctags lookups.
  I don't want to exactly copy its interface, though.
* `FT` allows looking up symbol names,
  definitions and references.
* ctags will be supported via ctags-lsp.
  LSP support is more powerful though and works without
  regenerating TAGS files all the time.
  The LSP will also allow you to customize auto-completions
  using SciTECO itself (i.e. by writing a language server
  in SciTECO).
* For multiple results, `FT$` can be used to cycle through
  results - this should mimic repeated `S$` or `N$`.
* `:FT...$` does a fuzzy search. IMHO it's not important
  to return a status integer instead. `FT` will only
  really be used in interactive mode.
* Document synchronization is supported via hooks from
  ring.c and via Scintilla notifications.
* Currently, the LSP communication is based on blocking
  GIOChannels. This means that a misbehaving hanging
  server could "lock up" the entire editor (FIXME).
  Only on ncurses you can always kill the subprocess by
  pressing CTRL+C.
  We need helper functions in spawn.c to read and write
  with interruptions.
* The textDocument/didChange notification transmits
  not only all edits, but all files' contents as well
  during initial synchronization.
  Therefore it is optimized to write and JSON-escape
  data without copying them around in memory and without
  destroying the buffer gap.
* Use $SCITECO_LSP to configure the language server.
  You can also use `tee` to capture stdin and stdout.
  Perhaps $SCITECO_LSP should be saved in .teco_session,
  so you can change it between projects?
* $SCITECO_LSP_ROOT is used to point to the project's
  root directory. session.tes will set it up automatically.

It will be useful for implementing LSP support.
It does not have JSON escape/unescape functions, so those
will still have to be written.

Source: https://github.com/rxi/sj.h

This is useful when writing small macros directly on the
command-line as in `sciteco --eval`. If you use double quoted shell
strings, too many characters have to be escaped.
If you use single-quotes, though, embedding the conditional end (')
is annoying -- it would have to be written as '\''.

Inlining the macro calls no longer results in a 25% speedup.