tex-luaotfload{,-doc} update to 3.17

2020-09-02 luaotfload v3.15
* The font database is updated more reliably if fonts get deleted.
* In multiple error cases, error messages are shown instead of silently
  generating bad output.
* Write glyph ids instead of internal identifiers to DVI files. This
  allows using OpenType fonts when working with dvilualatex.
  (This requires additional support from the DVI reader)
* The set of font features which are enabled by default has been
  changed to be more similar to HarfBuzz.
  Especially Above-base mark Positioning (abvm),
  Below-base mark Positioning (blwm), Contextual
  Alternates (calt), Cursive Positioning (curs),
  Distances (dist), and Required Contextual Alternates
  (rclt) are now enabled by default for all scripts.
* Added a mathfontdimen font feature which allows emulating
  fontdimen values from xetex or traditional TeX math fonts.
* Initial support for variable fonts in node mode.
2020-12-30 luaotfload v3.16
*  The fontloader has been synced with the context code from
2020-12-30
*  The entry point is called luaotfload.lua instead of
    luaotfload-main.lua (but the old name is still provided for
    compatibility).
*  pre/post_shaping_filter callbacks has been added.
*  The number of lua-files and submodules shown in the log-file
    has been reduced. But it is extended again by setting the
environment variable LUAOTFLOAD_TRACE_SUBMODULES=1.
*  The HarfBuzz based shaper will in some situations drop
hyphenation points. This happens less frequently now since the new
version uses first/second discretionaries (the mechanism described in
the LuaTeX manual, section 5.6 for the of-f-ice example) to support a
limited amount of nesting.
*  When the node shaper is used, experimental support for
    OpenType variable fonts has been added. To use them, set the
font feature axis to a comma separated list of axis names and values.
    (E.g.  axis={weight=600}) The supported axis names and value
    range depend on the font.
*  The font features upper and lower can be used to map
    the text of a font to upper or lowercase before displaying it.
Currently this implements the untailored Unicode case mapping
algorithm, but it is planned to add tailoring later.
*  A number of small bugfixes.
2021-01-08 luaotfload v3.17
*  The fontloader has been synced with the context code from 2021-01-07.
    This improves support for advanced CFF based OpenType variable fonts.

(markd)