Fix VertexList.migrate by clearing region caches.
Fix VertexList.migrate by clearing region caches.

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