Tategaki does not ignore orientation rotation, instead it always
rotates affect glyphs by 90 degrees inside their cell.

As far as I'm aware this just works, I'm not aware of any open issues related
to it.

Since we already implement it. Tweening will likely never work with fixed
function GL.

We can just do this in context_create_fbo_entry() now.

The draw buffer handling code depends on this being current. This fixes a bug
exposed by commit 075fa654.