Pull for "Rainbows, Droids & Compute Hippies"

* Basic GPGPU compute support via GPUmat.
* Nexus-7 / ARM support.
* Linux multi display backend support.
* Bits# support.
* PR-705 support.
* GeForce-600 series support.
* Fixes for OSX timestamping brokeness and other bugs.
* Various smaller fixes and improvements.