Screen Linux/OSX: Add special case support for AMD DCE-3 display engine.

Turns out AMD’s R700 chips (= roughly HD4000 series cards) do have
their own type of display engine, something i overlooked so far: The
DCE-3 engine is mostly like the old DCE2/DCE1 AVIVO engine, but the
setup and configuration of encoders and transmitters is different and
some regs were therefore moved. Particularly dithering and output bit
truncation is no longer setup per encoder/transmitter, but per crtc.

Add detection logic for DCE-3 engine and special case handling for
display dithering control for the DCE-3 case in both Linux
PsychScreenGlue. c and the PsychtoolboxKernelDriver.cpp.

-> This means that likely PTB had no control over dithering en/disable
on HD-4000 series cards, unless the old register locations are somehow
magically mirrored onto the new ones in hardware.

-> Add some OSX + AMD HD4000 / DCE-3 specific test code into
Screen(‘Null’) to test some hypothesis.

-> Screen for 64-Bit Matlab on OSX rebuilt.
Screen/PsychtoolboxKernelDriver: Fix DCE-1/2 AVIVO display engine dither control for multi-display.

Our assumption about bit depth/dither control on DCE-1/2 engines for
multi-display setups was wrong.
It’s not the case that one encoder drives all DVI/HDMI outputs, so
dither control is global.
Instead there is one TMDS block for one DVI-D / HDMI port and then
there is a LVTMA block, which can be reconfigured to either drive LVDS
or DVI-D or HDMI.
This makes mapping of crtc’s to encoders more difficult for selection
of the proper block config register to control per crtc output
dithering and bit truncation.
Now we probe each available hw block if it is enabled and sourcing from
our crtc (headId) and thereby find the proper target block for
configuration. This should make old Radeon X1000/HD2000/HD3000 series
gpu’s robust wrt. dual-display setups with need to disable dithering
for high bit depth display.

These are backwards incompatible changes, also wrt. different DCE1/2
vs. DCE3 treatment.
Bump the kernel driver revision number on OSX from 0 to 1 and make sure
Screen() on OSX only accepts driver revision 1 and rejects old rev 0
drivers with some notice to user to upgrade asap.

-> PsychtoolboxKernelDriver64Bit and 64Bit-Legacy rebuilt.
-> Screen rebuilt for OSX and basic testing.
-> Screen for Linux rebuild and test pending.