Screen: Add lossless 16 bpc movie writing/recording support.

This allows to write 16 bpc grayscale and RGB movies vie
Screen(‘CreateMovie’) and the dc1394 video capture/recording engine, by
extending the GStreamer movie writing backend. I couldn’t find any
suitable 16 bpc capable codecs in GStreamer-0.10, so we define our own
proprietary format for this purpose, which can only be read/processed
by PTB, so it is only suitable as an intermediate format. We pack 16
bpc pixels into 8 bpc lossless encoded rgb pixels. For 3 channel we
store high/low bytes of 16 bpc RGB in adjacent RGB8 pixels, using a
double-wide image format. For 1 channels, we store high/low bytes of
successive 16 bpc gray pixels in [RG, B][R, GB] channels of RGB8
pxixels, so 2/3 of RGB8 pixels are needed to store a given number of 16
bit grayscale values. Accomplish this by reducing height of encoded
video to 2/3 the height of input video. A new keyword for movie
encoding options named ‘'UsePTB16BPC’ enables encoding/recordig of such
movies. A new specialFlags1 setting 512 in movie playback’s
Screen(‘Openmovie’) call allows decoding of such movies.

-> LosslessMovieWritingTest.m extended to test proprietary ptb 16 bpc
movie writing.
-> Screen for 64-Bit Matlab on OSX rebuilt and tested.
-> Provides fully lossless 8 bpc and 16 bpc movie encoding with
suitable codecs like huffyuv (aka ffenc_huffyuv) and ffenc_sgi.
-> This is probably as good as it gets for the eol’d GStreamer-0.10
series wrt. to high bit depth support.
-> On synthetic test images, even compressed lossless movies are
slightly larger than raw data would be, about 10% larger. On real
footage this may be a bit better.
-> Performance testing with libdc1394 video capture+recording is tbd.