SetCompressedStereoSideBySideParameters(): Adapt to use with panelfitter.

-> Use raw width/height of window, not scaled size.
-> Makes ImagingStereoDemo(102) work with panelfitter on.
PsychDataPixx: Fix 'En/Disable''BlueLine/ScanningBacklight' on old Datapixx files.

Was still the wrong way to skip setup of unsupported functions.
Now should work. Tested on 64-Bit Octave on Linux, for which we
don't have updated Datapixx mex files yet.