Screen: Robustness enhancements for AMD 10 bpc framebuffer mode + stereomode 10.

It is not clear if these are really needed. Tests by Nicolas Cottaris
on a 10 bpc frame buffer, dual-windows, dual-display, stereo mode 10
stereo setup under OSX 10.8.5 with AMD HD 4870 + 2 DVI outputs and DVI
-> HDMI converter dongles show no difference between Screen() from the
30-Dec-2013 beta, and the Screen mex file from this commit. So these
enhancements may very well be not needed, but they don’t hurt either
and could potentially improve stability in corner cases.

-> PsychFixupNative10BitFramebufferEnable…() now also rewrites the
LUT-Bypass-Control bits, although AMD docs suggest this is not needed.
But anyway, no harm done.
-> PsychFixup… allows additional debug output at verbosity 10 about the
state of the control regs before fixup, to see if anything gets screwed
up. So far testing indicates, it doesn’t, at least not on OSX 10.8.5
for dual-window setup and flips.
-> PsychPreFlipOperations now does additional calls to PsychFixup… for
both the master and slave stereo window in stereo mode 10. Seems to be
not needed either, but shouldn’t hurt. Also stereo mode 10 is only used
on OSX, as other OS’es have better means to handle stereo.

-> Screen for 64-Bit Matlab on OSX rebuilt and tested by Nicolas.