Issue 231: insert glFlush after glTexImage transfers before source buffer is collected.
Issue 231: insert glFlush after glTexImage transfers before source buffer is
collected.

niklaskorz/pyglet,adamlwgriffiths/Pyglet,niklaskorz/pyglet,seeminglee/pyglet64,adamlwgriffiths/Pyglet,seeminglee/pyglet64,niklaskorz/pyglet,adamlwgriffiths/Pyglet,niklaskorz/pyglet,adamlwgriffiths/Pyglet,seeminglee/pyglet64