[gtk/matthiasc/for-master] (23 commits) ...Add GtkOverlayLayout to the docs

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  ca1c570... gtk-demo: Stop using appmenu apis (*)
  6c31092... examples: Stop using appmenu apis (*)
  a8df81b... inspector: Drop app-menu support (*)
  d5da3b9... print-editor: Stop using appmenu apis (*)
  79d6a77... gtkapplication: Drop app menu support (*)
  1038b9b... docs: Mention app menus in the migration guide (*)
  5e25ba6... Merge branch 'no-app-menu' into 'master' (*)
  ffa5334... Merge branch 'matthiasc/for-master' into 'master' (*)
  3e68c69... Update Turkish translation (*)
  0606dd5... Update Romanian translation (*)
  f1e3581... Update Romanian translation (*)
  be8fc8f... Update Polish translation (*)
  2e27a76... applicationwindow: Stop querying shadow width (*)
  48c9c86... window: Remove private _get_shadow_width() (*)
  6090248... applicationwindow: Simplify measure implementation (*)
  23e68c0... gl renderer: Cache whether clips is rectilinear (*)
  094788f... gl renderer: Refactor render_clipped_child (*)
  d5bf3c2... gl renderer: Improve clipping code (*)
  04b7dd8... compare-render: Fix some memory leaks (*)
  2127cc1... adwaita: move backdrop box shadows to .csd (*)
  5317e4b... constraint-editor: Don't use g_type_ensure
  9fa3742... Make GtkOverlayLayout public
  e4623fd... Add GtkOverlayLayout to the docs

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