fixing end overwrite bugs (some at least)
this needs testing, untested parts should be reversed before release
i tested 24->32, 15->16, bgr24->rgb, bgr32->rgb (retesting them isnt a bad idea either ...)


git-svn-id: file:///var/local/repositories/mplayer/trunk/postproc@6097 b3059339-0415-0410-9bf9-f77b7e298cf2