[gtk] (4 commits) Non-fast-forward update to branch image-loading

[Matthias Clasen <matthiasc src gnome org>]

The branch 'image-loading' 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:

  811872e... Add contentserializer tests for textures
  be48cbd... Add code to load jpegs
  4a2f668... Load jpegs without gdk-pixbuf
  ed2b3d7... Add tests for the jpeg loader

Commits added to the branch:

  4fffa68... Add contentserializer tests for textures
  3abb7e1... Add code to load jpegs
  e20106a... Load jpegs without gdk-pixbuf
  13f4e50... Add tests for the jpeg loader