[gtk] (11 commits) ...Merge branch 'child-properties' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  4a1019b... popover menu: Add an api for adding submenus (*)
  5c26976... popover menu: Drop the submenu child property (*)
  8c80730... builder-tool: Rewrite GtkPopoverMenu::submenu (*)
  14ad26a... Convert ui files (*)
  a443145... toolbar: Remove the homogeneous and expand child properties (*)
  7e88fcf... builder-tool: Rewrite toolbar child properties (*)
  6b050a2... Convert ui files (*)
  26de69e... paned: Replace the child properties (*)
  3631878... builder-tool: Rewrite paned child properties (*)
  396deb4... Convert ui files (*)
  dec2cf4... Merge branch 'child-properties' into 'master'

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