[gtksourceview] (9 commits) ...Merge branch 'jefferyto/gtksourceview-css-cleanup'

[Christian Hergert <chergert src gnome org>]

Summary of changes:

  7cae0c0... css.lang: Fix digits not allowed in vendor-specific prefix
  1f50e98... css.lang (and family): Clean up regular expression groups
  96d4b2f... css.lang (and family): Invert identifier character classes
  4fc20f8... css.lang (and family): Replace word boundaries with custom 
  ce43d9a... css.lang (and family): Set prefix/suffix for keyword contex
  41a2697... css.lang: Remove duplicate keywords
  b0a0469... less.lang: Fix :extend() not highlighted inside rulesets
  2abc628... css.lang (and family): Update copyright
  de87471... Merge branch 'jefferyto/gtksourceview-css-cleanup'