SetAnaglyphStereoParameters: Make overlay setup slightly less broken.

It's still pretty broken for anything but stereomodes 4-9, but at least
those work, sort of. Doing this properly would require a much less
simple approach.
Make imaging pipeline display compatible with panelfitter scaled modes.

Modified setup code in BitsPlusPlus.m and PsychImaging.m to enable
proper stimulus display if the imaging pipelines panelfitter is active
and the windows clientRect therefore doesn't correspond to the windows
actual framebuffer size (rect).
RemapMouse(): Make compatible with our gpu-based panelfitter.
PsychStartup.m: Make GStreamer SDK detection more robust.

Don't trust SDK installdir environment variable blindly, but
double-check if the SDK is where it is claimed to be.

Add more fallback probes: Check drives C,D,E,F,G for standard
installation path, now with the 0.10 version name instead of 2012.9,
2012.11 etc. The legacy probes for 2012.5 and 2012.7 remain.
PsychImaging: Implement PsychImaging('UsePanelFitter')

Implement full high-level setup for our panelfitter. Provides all the
high-level scaling modes of typical panel fitters and then some extras.

This should complete the gpu panelfitter implementation for our image
processing pipeline.
Merge branch 'master' of https://github.com/kleinerm/Psychtoolbox-3
BeampositionTest: Add help text, tweak Ian's improvements.

Make sure the histogram has a bin for each possible scanline from 0 to
VBL endline, so we can see certain "bug patterns".

Make sure it doesn't hang if beampositions are totally broken.

Add help text.

Also update "Help PsychTests" with entry for BeampositionTest.
BitsPlusPlus: Make sure overlay texture is nearest neighbour filtered.

Not really needed, as this is the default, but avoids confusion during
debugging.
AdditiveBlendingForLinearSuperpositonTutorial: Disable text anti-aliasing for hardware overlay.

Otherwise mk gets confused by anti-aliasing artifacts if Datapixx et
al. or Bits+ et al. are driven with hw overlays on.
ImagingStereoDemo: Add a snippet of (disabled) Panelfitter demo code.

Just there for reference, but commented out by default.