cairo: enable multithreading for cairo-xlib

We want to be able to free cairo objects from the background thread,
and that means we must be able to make xlib calls from multiple
threads. Which is ok, if we initialize xlib beforehand.

We don't have a good place to initialize gjs, where we're sure to
be called before the first XOpenDisplay(), so just stuff it into
a constructor.

https://bugzilla.gnome.org/show_bug.cgi?id=730030
Release 1.41.3

For GNOME 3.13.3
Post-release version bump to 1.41.4