* This is a very big blunt hammer for fixing the problem of multithreaded
submission from GL. Every GL call checks to see if the context changed (which
would only happen from a thread switch to a different context) and if detected
it inserts a manual MakeCurrent call equivalent.
* It's slow to capture (when this happens - checking is not particularly slow)
and slow to replay, but it's functional which is an improvement.
baldurk