swap_eyes configuration has no effect on dual-screen displays

[russell-taylor]

This is eventually read inside RenderManager code using getSwapEyes(), which is only being used to determine the viewports for when we render both eyes into the same output buffer.

It should also be checked when doing each eye into its own output buffer.

[russell-taylor]

Fixed in 1ad31814ea25eea79f13f7b1dd99d92a42e8686c