Very many testcases, some GLib tools (resource compiler, etc) and
GApplication were calling g_type_init().
Remove those uses, as they are no longer required.
https://bugzilla.gnome.org/show_bug.cgi?id=686161
.. and add a C setter to do this. Also make the C getter return a
reference since the property may be set from another thread. Also
change the constructor to _not_ take a GDBusConnection since this is
something you almost always want to do _after_ creating it. The
API/ABI break is fine as there has never been a GLib release with this
type.
https://bugzilla.gnome.org/show_bug.cgi?id=648959
Signed-off-by: David Zeuthen <davidz@redhat.com>
