Add support for grabbing frames from the PSEye camera by using the PS3EYEDriver and libusb on OS X. This needs to be enabled separately in CMake. By default, it tries to find libusb from the system (via pkg-config), but there's also support for building libusb-1.0.9 (in external/) statically and linking against it statically. Static linking is also what contrib/build-osx-snapshot uses now. This means that the iSight isn't supported for those snapshot builds, you would have to disable the configuration options in the script and rebuild without PSMOVE_USE_PS3EYE_DRIVER (you can also skip building libusb in this case). The frames read from the USB camera are encoded in YUV422 format, we currently convert this using a function from PS3EYEDriver, modified to output BGR data instead of RGBA. By using multithreading and better buffer management (or buffer management at all), the frame rate could definitely be improved, but this is not implemented yet. Tested with OS X 10.9.1, but older releases should also work.
We now have API function calls to set the dimming factor from the user application, which allows for dynamic modification of the dimming factor.