Kill the global references in the OpenGL wrappers.

Just use jniThrowException instead. Note that it would be trivial to throw
seemingly more appropriate exceptions (NullPointerException and
OutOfMemoryException in particular), but I'm only attempting to preserve
existing behavior here.

I also found shadowing bugs in some of the special-case functions, which
would previously always have leaked memory.

This also moves an accidental change to a generated file (ActivityThread ->
AppGlobals) into the generator, so it won't be overwritten in future.

Change-Id: Iab570310b568cb406c60dd0e2b8211f8a36ae590