* Support fold level configuration using `.SCITECO_FOLDLEVEL`.
  This sets the current output line as the fold header and all subsequent lines
  with the given fold level (until another `.SCITECO_FOLDLEVEL` instruction
  is encountered).
* This is now done automatically for man's SH and SS macros,
  so the man-page based woman pages provide folding.
* The folding margin is therefore now always enabled in fallback.teco_ini.

* This is rendered with ms, so we now need the entire groff on Debian.
  This is not a big deal as it just adds a few kilobytes of build-time dependencies.
  Most platforms do not allow installation of some "groff-base" package anyway
  and always draw in the entire package.
* sciteco.tmac has been extended to disable page breaks on ms.
* The tutorial is installed like any other woman page and can be invoked
  interactively with ?tutorial$.
* It is optimized to be still usable on a plain 80x24 terminal.

This could theoretically be used to apply Scintilla styles not natively and easily supported by grosciteco,
eg. different fonts and font sizes.

* Hopefully disables paragraph breaking in newer Groff versions,
  but needs to be tested.

 * fixes manpages, Groff warnings and building
   womanpages for older Groff versions.
   Groff v1.19 is in use eg. on FreeBSD 11.
 * tbl v1.19 has different column specifiers than
   on later versions. `X` cannot be used for expanded
   columns in these Groff versions.

 * we had an undocumented dependency on Groff v1.20, since
   this version introduced the .device request.
 * this broke the womanpage generation e.g. on OS X 10.6.
   Even newer versions of OS X only appear to ship Groff v1.19.
 * Since it makes sense to support the Groff shipping with OS X,
   we work around this issue by reimplementing .device on platforms
   that lack it.
 * The fallback implementation still has subtle differences to
   the real .device, but they are acceptable for the time being.

 * the new "?" (help) command can be used to look up
   help topics.
 * help topics are index from $SCITECOPATH/women/*.woman.tec
   files.
 * looking up a help topic opens the corresponding "womanpage"
   and jumps to the position of the topic (it acts like an anchor
   into the document).
 * styling is performed by *.woman.tec files.
 * Setting up the Scintilla view and munging the *.tec file
   is performed by the new "woman.tes" lexer.
   On supporting UIs (Gtk), womanpages are shown in a variable-width
   font.
 * Woman pages are usually not hand-written, but generated from manpages.
   A special Groff post-processor grosciteco has been introduced for this
   purpose. It is much like grotty, but can output SciTECO macros for styling
   the document (ie. the *.woman.tec files).
   It is documented in its own man-page.
 * grosciteco also introduces sciteco.tmac - special Troff macros
   for controlling the formatting of the document in SciTECO.
   It also defines .SCITECO_TOPIC which can be used to mark up
   help topics/terms in Troff markup.
 * Woman pages are generated/formatted by grosciteco at compile-time, so
   they will work on platforms without Groff (ie. as on windows).
 * Groff has been added as a hard compile-time requirement.
 * The sciteco(1) and sciteco(7) man pages have been augmented with
   help topic anchors.