Screen: Add fallback for use of panel-fitter on gpu's without blit support.

If glBlitFramebuffer() is not supported on a gpu+driver combo, but use of
panel-fitter is requested, we used to fail. Now we have a fallback which
uses our normal PsychBlitterIdentity() with some tweaked destination offset,
scale, size to blit the drawBufferFBO texture into the inputBufferFBO,
thereby implementing the fitter. Works now on OpenGL-ES1 api.

Some restrictions for fallback: No multisample anti-aliasing (no MSAA resolve),
some fitting modes don't work - If the srcRect != clientRect, distortion
happens, because our (ab)used texture identity blitter does not support
non-default srcRect selection -- always blits the full texture ergo full
drawBufferFBO. Screen() warns, if an unsupportable configuration is chosen
and the fallback is in use.
Screen: Make 3d rendering with imaging pipeline more robust.

Allow PsychCreateFBO to always fall back to renderbuffer depth and
stencil attachments, so it can handle complete lack of depth textures
not only in MSAA case, but also for aliased rendering.

Add fallbacks for depth/stencil renderbuffers for 24 bit -> 16 bit depth
and 8 bit -> 4 bit stencil to cope with some very limited OpenGL-ES
implementations.

Some cleanup of status messages as well.
Modify MorphDemo for testing of 3D rendering + imaging pipeline.

-> While the code thinks it succeeds with setup on nouveau + GeForce gpu
   under OpenGL-ES 1.1, ie., none of the error handlers trigger, the
   bit depths of the resulting attached z/stencil renderbuffers are
   reported as 0 bits, and this is consistent with rendering artifacts
   observed in MorphDemo. Let's see on Tegra-3 how it behaves there.