[gtk+] (11 commits) Non-fast-forward update to branch wip/native-file-chooser

[Alexander Larsson <alexl src gnome org>]

The branch 'wip/native-file-chooser' 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:

  d89f51b... TreeModelFilter: Fix uninitialized memory read.
  3b5f950... Make GtkFileChooser interface require a GObject
  e675949... Add GtkNativeDialog abstract base class
  d1dfb9f... GtkFileFilter: Add private function to represent filter as 
  6997985... GtkFileChooserNative: Fallback and win32 implementation
  164f90b... GtkFileChooserButton: Use native dialogs
  afc5926... testgtk: Add native dialog tests

Commits added to the branch:

  c59ef7b... stack switcher: Clarify CSS documentation (*)
  87deb25... stack sidebar: Drop the .sidebar-item style class (*)
  66d2c9e... Adwaita: Update stack sidebar styling (*)
  4d524ab... widget: Avoid critical warnings when disconnecting plain Gt (*)
  455064d... TreeModelFilter: Fix uninitialized memory read.
  48575e0... Make GtkFileChooser interface require a GObject
  e4c9e3a... Add GtkNativeDialog abstract base class
  ab9392b... GtkFileFilter: Add private function to represent filter as 
  e0ad8a8... GtkFileChooserNative: Fallback and win32 implementation
  edcab8c... GtkFileChooserButton: Use native dialogs
  f036676... testgtk: Add native dialog tests

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