This will allow some color keying cleanups. For Core Contexts we'll have
to emulate alpha testing in shaders anyway.

This is necessary if e.g. the nvts or ffp fragment processing pipeline
is selected for debugging purposes on a GPU that otherwise supports the
ARB program blitter.

Based on original patch by Nikos Mavrogiannopoulos.

As soon as SO_ERROR is read from getsockopt it is reset in the kernel,
when attempting a non-blocking connection the wine server reads
SO_ERROR first so when the application tries to read the value it will
end with zero.

Should fix the graphical corruptions recently introduced by
002713de.