[gtk] (25 commits) ...Merge branch 'matthiasc/for-master' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  0a3b370... Cosmetics (*)
  13b9b9b... scale: Set round-digits to -1 initially (*)
  37d4932... a11y: Add more tests (*)
  09eda80... docs: Add GtkWindowControls to the gallery (*)
  86b4b2e... docs: Fix links from the gallery (*)
  b7728a8... docs: Tweak gallery ordering (*)
  163d32e... docs: Work around GtkPicture growing (*)
  b0fb31f... docs: Some reordering in the gallery (*)
  2e0822b... docs: Shrink the editable label gallery image (*)
  a9f0f18... docs: Tweak gallery layout (*)
  64e131f... docs: Improve the GtkVideo gallery image (*)
  28b7962... docs: Improve the GtkMediaControls gallery image (*)
  dffe6b8... docs: Add GtkCalendar to the gallery (*)
  a70c9c6... docs: Fix the GtkVolumeButton gallery image (*)
  59e08c0... docs: Tweak gallery layout (*)
  291c618... docs: Improve the GtkStackSidebar gallery image (*)
  42e2c54... docs: Redo the GtkColorChooserDialog gallery image (*)
  8692f5d... docs: Add GtkEmojiChooser to the gallery (*)
  1605ca0... docs: Add GtkExpander to the gallery (*)
  bed3616... docs: Add GtkPopoverMenuBar to the gallery (*)
  65f748f... docs: Add GtkPopover to the widget gallery (*)
  d9259fc... docs: Add GtkPopoverMenu to the widget gallery (*)
  b67eee5... docs: Add GtkShortcutsWindow to the widget gallery (*)
  e51a98d... docs: Add GtkDrawingArea to the gallery (*)
  4661f15... Merge branch 'matthiasc/for-master' into 'master'

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