[devhelp] (3 commits) Non-fast-forward update to branch wip/swilmet/maintenance

[Sébastien Wilmet <swilmet src gnome org>]

The branch 'wip/swilmet/maintenance' 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:

  4f9193b... book-manager: remove useless function prototypes
  f077fe5... book-manager: unref objects in dispose()

Commits added to the branch:

  8036e2e... book-manager: spring clean-up
  dd4d1d6... book-manager: unref objects in dispose()
  8523fd6... book-manager: avoid O(N^2) time complexities