[gtk] (7 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:

  be6bd7f... Add gdk_texture_save_to_file
  9a9950e... Use our png loader for content (de)serialization
  4b546ef... Use our tiff loader for content (de)serialization
  3fef570... Add contentserializer tests for textures
  750149a... Add code to load jpegs
  e496984... Load jpegs without gdk-pixbuf
  d4dd8c1... Add tests for the jpeg loader

Commits added to the branch:

  f51ae83... Add gdk_texture_save_to_tiff
  30afe52... Use our png loader for content (de)serialization
  40353f2... Use our tiff loader for content (de)serialization
  9986373... Add contentserializer tests for textures
  59b0b40... Add code to load jpegs
  6f67efd... Load jpegs without gdk-pixbuf
  964556a... Add tests for the jpeg loader