[gtk] (9 commits) ...Merge branch 'wip/otte/widgetfactory-dnd' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  f5dc710... dnd: Guard drags with a reference when finishing (*)
  6a5d555... contentformats: Change the format of gdk_content_formats_to (*)
  131be5f... contentformats: Add gdk_content_formats_parse() (*)
  d760332... testsuite: Add contentformat tests (*)
  0781429... builder: Add support for GdkContentFormats (*)
  192bfa1... droptarget: Make formats construct-only writable (*)
  4453597... widget-factory: Some new backgrounds (*)
  f1b50ba... widget-factory: Add images that support dnd (*)
  910f23e... Merge branch 'wip/otte/widgetfactory-dnd' into 'master'

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