PTB BETA RELEASE "Hammertime!" SP4 - "Deadlock"

* XLib threading fixes for regressions introduced into Linux PTB.
* Make DaqDeviceIndex a bit more robust on OSX.
* Make IsomerizationInEye/DishDemo work again on Octave and fix some bugs.
* Reenable parts of PsychCV for 64-Bit Octave on Linux. (Experimental)