additionallym deprecate palette8torgb16 and its bgr variant without
replacement. These functions are not meant to be used by applications.

Discussed at: http://comments.gmane.org/gmane.comp.video.ffmpeg.devel/109340


git-svn-id: file:///var/local/repositories/mplayer/trunk/libswscale@31301 b3059339-0415-0410-9bf9-f77b7e298cf2