Actually calling cogl_set_default_context isn't required because
cogl_context_new implicitly sets the new context to be the default
context. Since we want to eventually get rid of the concept of a default
context we'd rather not pollute the example with the concept.
This adds Cogl API to show and hide onscreen framebuffers. We don't want
to go too far down the road of abstracting window system APIs with Cogl
since that would be out of its scope but the previous idea that we would
automatically map framebuffers on allocation except for those made from
foreign windows wasn't good enough. The problem is that we don't want to
make Clutter always create stages from foreign windows but with the
automatic map semantics then Clutter doesn't get an opportunity to
select for all the events it requires before mapping. This meant that we
wouldn't be delivered a mouse enter event for windows mapped underneath
the cursor which would break Clutters handling of button press events.
This adds a simple standalone Cogl application that can be used to
smoke test a standalone build of Cogl without Clutter.
This also adds an x11-foreign app that shows how a toolkit can ask Cogl
to draw to an X Window that it owns instead of Cogl being responsible
for automatically creating and mapping an X Window for CoglOnscreen.
