[gtk] (6 commits) Non-fast-forward update to branch wip/alexl/gl-debug

[Alexander Larsson <alexl src gnome org>]

The branch 'wip/alexl/gl-debug' 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:

  794dc9b... GdkGLContext: Add internal functions for KHR_DEBUG calls
  c3d487e... GskGLRenderer: Label various gl objects
  bf41845... GskGLRenderer: Add debug groups

Commits added to the branch:

  28815bc... Updated Spanish translation (*)
  34fcfb1... gl renderer: Properly apply opacity in cross-fade shader (*)
  91bbe6e... gl renderer: Sync gpu and cpu default alpha value (*)
  ab22130... GdkGLContext: Add internal functions for KHR_DEBUG calls
  edea772... GskGLRenderer: Label various gl objects
  7e823ff... GskGLRenderer: Add debug groups

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