PlayMoviesDemo: Another tweak to network streaming, another Musk talk.
LoadIdentityClut: Always call PsychGPUControl() to disable dithering.

This is only supported on Linux and Windows with recent AMD/ATI GPU's
and the proprietary Catalyst display driver, a silent no-op on other
system configurations. If successfull, it should disable display
dithering on all supported gpu's on all displays. Still most of our
remaining setup code must run, because we have no way of knowing if
dither disable succeeded, and we still need to take care of identity
gamma table setup.

Anyway, maybe helps for latest trouble with Radeon HD 6000/7000 gpus
on MS-Windows.
Merge branch 'master' of https://github.com/kleinerm/Psychtoolbox-3