[gtk] (13 commits) ...Merge branch 'icon-fallback' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  6f82408... Add logging for icon fallback (*)
  44481d3... Make testsuite fail if we lack pixbuf loaders (*)
  c9b312c... icons: Add icons that are used in the inspector (*)
  6dcef28... icon: Add a printer icon (*)
  1ea2ea5... icons: Add system-run-symbolic (*)
  b5608e9... icons: Sync color-select-symbolic with Adwaita (*)
  4028bd5... widget-factory: Add emblem-shared-symbolic icon (*)
  5940de9... icontheme: Add gtk_icon_theme_has_gicon (*)
  23cb728... filechooser: Check that icons exist (*)
  775b45e... icons: Add text-x-generic (*)
  6ba4142... widget-factory: Drop two icons from the iconview (*)
  3ab0720... widget-factory: Add missing icons (*)
  f6f07ba... Merge branch 'icon-fallback' into 'master'

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