PsychtoolboxKernelDriver64Bit: Try to make it compatible with both OSX 10.8 and 10.9

This build changes the base SDK to the OSX 10.8 SDK and the deployment
target to OSX 10.8.
This should work on 10.8 and 10.9 and has been successfully tested to
work on 10.9.
Tests for 10.8 pending.
-> Xcode project and PsychtoolboxKernelDriver64Bit.kext.zip updated.
PsychtoolboxKernelDriver64BitLegacy.kext.zip: Restore to September 2013 state for OSX < 10.8 compat.

I can only build new versions of the driver for 10.8 and later - at
best.
Restore the legacy driver for 10.6 and 10.7 to the state of September
2013, the best we can do.
-> 10.6 and 10.7 will be permanently broken wrt. digital display
dithering on AMD pre-HD5000 hardware.
Merge pull request #190 from kleinerm/master

Pull - I from kleinerm for PTB BETA RELEASE "Sex, Lies and Video" SP1

Make PsychtoolboxKernelDriver64Bit work on OSX 10.8 and 10.9 - hopefully. Only tested on 10. 9 so far.
Revert legacy 64 bit driver to September 2013 state for use on 10.6 and 10.7.