[gtk] (40 commits) ...Merge branch 'image-loading' into 'master'

[Benjamin Otte <otte src gnome org>]

Summary of changes:

  66031fd... texture: Add error enum (*)
  f51f7f8... Add code to load and save pngs (*)
  a71877b... Load pngs without gdk-pixbuf (*)
  7949aaa... Save pngs without cairo (*)
  d6ce65f... Add tests for the png loader (*)
  d7c8f92... Add gdk_texture_save_to_png_bytes (*)
  a03594d... Add code to load and save tiff files (*)
  f925e12... Load tiffs without gdk-pixbuf (*)
  945c253... Add tests for the tiff loader (*)
  d30a029... Add gdk_texture_save_to_tiff (*)
  729ba81... Add code to load jpegs (*)
  daf29e1... Load jpegs without gdk-pixbuf (*)
  e30b4c6... Add tests for the jpeg loader (*)
  d27bc74... Use our own loaders for content (de)serialization (*)
  95a0c93... Add contentserializer tests for textures (*)
  5b82cf1... rendernodeparser: Use gdk_texture_save_to_png_bytes (*)
  c77b5c4... rendernodeparser: Avoid gdk_texture_new_for_pixbuf (*)
  b1bb7c3... texture: Add gdk_texture_save_to_tiff_bytes() (*)
  577bf10... testsuite: Add png and tiff methods (*)
  f2ca9eb... texture: Avoid pixbufs when loading resources (*)
  100b0bf... texture: Remove declaration for nonexisting function (*)
  2d3de86... texture: Split out type detection (*)
  679c93e... texture: Add private can_load() function (*)
  dcd873a... builder: create textures without pixbufs (*)
  729ad8e... cssimageurl: Just create a texture directly (*)
  fecb31b... builder: Stop using pixbufutils (*)
  e720f9d... Add code to save jpegs (*)
  14280b5... contentdeserializer: Use our on jpeg loader (*)
  b226478... Support 16bit formats in the png loader (*)
  a85f4ec... icontheme: Load textures directly when possible (*)
  b5da07f... icontheme: Use textures more (*)
  4fcf547... icontheme: Insist that people provide proper values (*)
  e58f70d... pixbufutils: Don't hardcode formats (*)
  b271a94... texture: Rework error enum (*)
  fae3284... texture: Refactor gdk_texture_new_from_bytes() (*)
  1b85b55... texture: Implement GIcon and GLoadableIcon (*)
  37a7c67... icontheme: Implement gtk_icon_theme_lookup_by_gicon() for t (*)
  0428d8c... examples: Use textures over pixbufs (*)
  3914ecb... gtk-demo: Use textures in listbox example (*)
  1d41dc7... Merge branch 'image-loading' into 'master'

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