Toggle mirroring; remove old libusb patch

This adds the ability to toggle depth and video stream mirroring via
freenect_set_depth_mirroring(freenect_device *dev, freenect_mirroring_flag flag);
freenect_set_video_mirroring(freenect_device *dev, freenect_mirroring_flag flag);

It also removes the libusb patch for OSX since it has been merged into upstream libusb.