Revert "Moved screen to be upright and centered in screen. Currently causes some games to crash, so it may be reverted. TODO: GPU-accelerated rendering of texture vs forcing flip?"

This reverts commit 4984b51e6da2e880848fcb21870856a12aa895d2.
Further reversions.
Moved GBA rendering to separate framebuffer. Implemented screen flipping in software for now. Fixes a large number of crashes.