[gtk] (12 commits) ...Merge branch 'matthiasc/for-master' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  de24b4f... cssshadowvalue: Add a parsing function (*)
  9770872... css: Implement the drop-shadow filter (*)
  a1f7073... Add tests for the css filter property (*)
  4e27de7... cssshadowvalue: Drop the underscore (*)
  5b8896f... cssshadowvalue: Add gtk_css_shadow_value_pop_snapshot (*)
  be3f352... cssshadowvalue: Add a parsing function (*)
  429dfcf... cssshadowvalue: Add a 'filter mode' (*)
  ea7185b... cssfiltervalue: Implement drop-shadows (*)
  cc6fcbf... cssfiltervalue: Fix blur filter interpretation (*)
  5f48764... cssfiltervalue: Reject invalid filters (*)
  bfc80c3... Add tests for the css filter property (*)
  e8c8be8... Merge branch 'matthiasc/for-master' into 'master'

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