[gtk] (8 commits) Non-fast-forward update to branch matthiasc/css-values

[Matthias Clasen <matthiasc src gnome org>]

The branch 'matthiasc/css-values' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  7e7b2d6... css: Use a singleton for builtin image values
  790c0b0... dimension: Improve the coverage of singletons
  0e6be85... Add opaque black singleton

Commits added to the branch:

  6034752... csssshadwovalue: Remove unused function prototype (*)
  8433eaa... cssshadowvalue: Treat one shadow like multiple shadows (*)
  7bd570e... css: Use a singleton for builtin image values
  97ad46a... dimension: Improve the coverage of singletons
  a02a577... Add opaque black singleton
  2213abd... css: Simplify compute for font features
  c4c77d4... css: Simplify compute for font variations
  68b3d21... dump css value stats

(*) This commit already existed in another branch; no separate mail sent