version 3.15.1
 - Substitute bindir and libexecdir in Makefile.am
   Rather than substituting the values of libexecdir and bindir during
   configure, which might include some unexpanded shell variables, expand
   and substitute them as targets in Makefile.am instead.

   https://bugzilla.gnome.org/show_bug.cgi?id=726095
 - Use AC_PROG_SED in configure.ac
 - Remove old marshaller header from doc ignore list
 - Use get_instance_private() instead of priv pointer
   Use the generated macro rather than storing a pointer to the private
   struct within the object.
 - Drop some trailing semicolons after macros
 - Use new-style private struct in CheeseCameraDevice
 - Use _get_instance_private() consistently in camera
   Use the new cheese_camera_get_instance_private() instead of the old
   macro.
 - Bump required Vala version for get_menu_by_id()
   Use the get the given menu from GtkApplication.
 - Refactor setup_camera() in CheeseWidget
   Remove superfluous prototype. Use GSettings convenience getters. Reduce
   scope of some variables.
 - Avoid using G_GNUC_CONST on _get_type()
   As the g_type_ensure() documentation notes, it is incorrect to mark a
   _get_type() method with G_GNUC_CONST, as it as a side effect the first
   time it is called.