Merge pull request #216 from kleinerm/master

PTB BETA RELEASE "Random acts of kindness" Psychtoolbox-3.0.12 - SP2

* Switch to OSX 10.10 Yosemite - SDK, support status now 10.10 only.
* Fix compatibility with 10.10 SDK, replace deprecated functions like Gestalt.
* PanelFitter/RemapMouse: Now handle also rotation.
* Some demo cleanups.
* Support for Retina displays (aka HiDPI) for OSX.

-> This is a "OSX only" update. No significant change to the other os'es.