[gtk] (12 commits) ...Merge branch 'action-muxer-speedup' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  aa76f7e... Speed up action muxer setup (*)
  ab67a81... Speed up action muxer setup more (*)
  07e8daf... inspector: Remove action support temporarily (*)
  14bb121... actionmuxer: Add some more api (*)
  4786a16... actionmuxer: Port internal users (*)
  96d42cf... actionmuxer: Stop implementing GActionGroup (*)
  9b294eb... Add gtk_action_muxer_list_actions (*)
  14059af... inspector: Make the actions tab work again (*)
  05e614f... actionmuxer: Create observed_actions and groups on demand (*)
  ed92026... actionmuxer: Use an array for accels (*)
  486fbce... actionmuxer: Update docs and clean up headers (*)
  ee9c6bb... Merge branch 'action-muxer-speedup' into 'master'

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