tex-polyglossia{,-doc}: update to 1.51

1.50
New features:
 * Polyglossia now uses the Harfbuzz renderer by default with LuaTeX
   output. This brings LuaTeX on par with XeTeX for all scripts.
   The renderer can be changed via the new global luatexrenderer
   option.
 * The (previously inadvertently working) hyphenrules environment that
   ceased to work after a recent babel update is back and now
   officially supported. The environment now also supports language
   options and aliases.
 * New command \setlanghyphenmins to adapt hyphenation thresholds of
   languages and varieties.
 * New command \abjadalph for Arabic with corresponding option.
 * Replace consecutive glues around punctuation by the correct amount
   of space with LuaLaTeX for French, ecclesiastic Latin, and Sanskrit.

1.50a
This is a minor release that fixes a regression with Russian and
some classes introduced in v. 1.50

1.51
New features:
  * New option "frenchpart" for French.
  * New option "splithyphens" for Croatian.

Bug fixes:
  * Use new LaTeX core hooks rather than filehook package. This fixes
    a recent breakage of filehook with other external packages.
  * Remove very old code that pretends polyglossia is babel.
  * Fix spelling of Albanian \contentsname.
  * Fix part heading modification in French.
  * Fix extra space in Hebrew.
  * Register main polyglossia language earlier.
  * Allow for hyphenations in words following opening guillemet in
    French with XeTeX.


(markd)