Adding Cinepak encoder

With permission of Tomas Härdin applied by Rl aetey.se

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/cinepakenc: fixes and improvements

Fixed/improved multistrip adaptivity.
Improved R/D by optimized codebook generation.
Support for the correct color space.
Vintage compatibility.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>