Remove the compiler bug notice.
window: add width/height setting constructor
window+camera: add variable passes, defaults to 1
add stereo side by side camera

make sure it works with shaders too, see examples/stereo.rs
oculus_stereo as a clone of wave without dt update

shader is loaded from a file so can be changed without recompiling.
Allow default keyboard handling on the stereo demo.
Remove an unnecessary clone.
Update the gl scissor when the viewport is resized.
Remove an useless variable from the oculus stereo post-processing effect.
Pass the homogeneous matrix by reference to the camera upload_mat method.