[gtk] (12 commits) Non-fast-forward update to branch wip/exalm/headerbar-title

[Alexander Mikhaylenko <alexm src gnome org>]

The branch 'wip/exalm/headerbar-title' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  d6d2646... headerbar: Remove has-subtitle property
  ac769be... appchooserdialog: Create title and subtitle manually
  aad6ac0... filechooserdialog: Create title and subtitle manually
  507609d... headerbar: Remove subtitle
  4ad6bdb... headerbar: Remove user-settable title
  b568eef... headerbar: Rename custom-title to title-widget
  8927cd5... builder-tool: Rename GtkHeaderBar:custom-title to title-wid

Commits added to the branch:

  cb056a1... stack: Add a :use-underline property (*)
  f31c85f... widget-factory: Add mnemonics to the stack pages (*)
  b1bedbc... widget-factory: Improve demo keynav (*)
  850549b... Merge branch 'matthiasc/for-master' into 'master' (*)
  43a453e... headerbar: Remove has-subtitle property
  67822d0... appchooserdialog: Create title and subtitle manually
  fa0509c... filechooserdialog: Create title and subtitle manually
  35d50f8... headerbar: Remove subtitle
  c2e4e1a... headerbar: Remove user-settable title
  739f681... headerbar: Rename custom-title to title-widget
  6b4bed2... builder-tool: Rename GtkHeaderBar:custom-title to title-wid
  b88e2f5... headerbar: Document GtkBuilder child types, add a title exa

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