Maintain different set of PsychtoolboxKernelDriver's for pre 10.9 vs. 10.9 and later.

Rename PsychtoolboxKernelDriver32Bit to
PsychtoolboxKernelDriver32BitLegacy to signal it is no longer
maintained status. Add back September 2013 64 bit PTKD as
PsychtoolboxKernelDriver64BitLegacy, as apparently our latest December
2013 driver is no longer compatible with OSX 10.8 and earlier. This one
is now also unmaintaned.

The PsychtoolboxKernelDriver64Bit.kext.zip is the only version still
maintained and it works on the 64-Bit kernels of OSX 10.9 and
(hopefully) later.