Also remove the tcgetattr check that is no longer used.

In preparation for WGL_EXT_swap_control_tear support, transition to using glXSwapIntervalEXT.

This is needed on FreeBSD 8.1.

We never render directly to the front buffer, and in case of e.g. a P8 front
buffer, we would fail surface creation if we were to enforce format
restrictions.

wined3d: Use clamp() instead of max() for calculating the clamped cosine in the ffp lighting calculations.

On typical hardware, the clamp() would be an instruction modifier, while the
max() would need an extra instruction.