[gtk] (18 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:

  2c6e890... Add code to load and save pngs
  43ceb17... Load pngs without gdk-pixbuf
  f43abcc... Save pngs without gdk-pixbuf
  6588a1d... Add tests for the png loader
  2cb047b... Add code to load and save tiff files
  7912033... Load tiffs without gdk-pixbuf
  6661eaa... Add tests for the tiff loader
  e519ca7... Add gdk_texture_save_to_tiff
  e357e0b... Use our png loader for content (de)serialization
  c2a89b1... Use our tiff loader for content (de)serialization
  22aaf57... Add contentserializer tests for textures
  4edec16... Add code to load jpegs
  4abc3f8... Load jpegs without gdk-pixbuf
  dc758b9... Add tests for the jpeg loader

Commits added to the branch:

  b9ee997... Update German translation (*)
  6785461... gltexture: Make sure downloading textures works in a differ (*)
  193b383... ngl: Simplify and unbug texture download (*)
  f572ca5... Merge branch 'wip/otte/texture-threads' into 'master' (*)
  59e7dbe... Add code to load and save pngs
  feacd4d... Load pngs without gdk-pixbuf
  de653d6... Save pngs without gdk-pixbuf
  714e847... Add tests for the png loader
  48af29f... Add code to load and save tiff files
  7c63a4a... Load tiffs without gdk-pixbuf
  9ad5f3a... Add tests for the tiff loader
  4990a5c... Add gdk_texture_save_to_tiff
  275c2c3... Use our png loader for content (de)serialization
  026f777... Use our tiff loader for content (de)serialization
  7a0c7cd... Add contentserializer tests for textures
  dc498fc... Add code to load jpegs
  962cf0f... Load jpegs without gdk-pixbuf
  7ed91bb... Add tests for the jpeg loader

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