Psychtoolbox core: Raise limit for max number of subfunctions to 256.

Old limit was 128, which would get exceeded by current Datapixx mex
file, which is around 140 subfuntions. Double to a safe 256 maximum.
Add build script for Datapixx mex file.

datapixxmakemex.m is a modified version of the M-Makefile
used by VPixx to build the Datapixx mex files for the different
runtime + OS combos.

Adapted to Psychtoolbox 3.0.12 and MK's build system:

- Different base pathes to Psychtoolbox and ViewPixx toolbox
  source code.

- Adapt for 64-Bit builds on all os'es where needed.

- Drop some unneeded code, e.g., for PsychScriptingGlue.cc

- Add linker flags for building on OSX + Octave.

-> This script is so far tested by rebuilding for 32-Bit Octave on Linux
   and first time support for building on 64-Bit Octave on OSX.

-> Not tested for 64-Bit Octave on Linux or Matlab mex files yet,
   as at least the Matlab mex files likely won't need a rebuild
   for this initial 3.0.12 release.
Add up to date Datapixx mex files for all but 64-Bit Octave on Linux.

-> 64-Bit Octave mex file for Linux needs rebuild after reboot.
-> 64-Bit Matlab mex file for Linux needs compatibility test after reboot.
-> 64-Bit Matlab mex file for Windows and OSX taken from VPixx release.
-> 64-Bit Octave mex file for OSX rebuild against OSX 10.9.5 SDK
-> 32-Bit Octave mex file for Linux rebuild against Ubuntu 14.04-LTS.

-> Octave mex files are quite outdated in VPixx's official release
   and do/did need rebuild from their LGPL-2 sources.

-> Matlab mex files are up to date (March 2014, PTB 3.0.11) enough
   and won't get rebuild.