[gtk] (2 commits) Non-fast-forward update to branch wip/chergert/fix-class-private-data-usage

[Christian Hergert <chergert src gnome org>]

The branch 'wip/chergert/fix-class-private-data-usage' 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:

  8d1588a... gtk: add bitarray for use by widget muxer
  a4a8453... widget: move class private data to gtkwidgetprivate.h
  7a7e4e1... widget: fix class private data usage to be _init() safe

Commits added to the branch:

  4401d5c... widget: move class private data to gtkwidgetprivate.h
  4f33065... widget: fix class private data usage to be _init() safe