to a float within [0.0, 1.0] and later multiplied by 256.0 to convert
back. This makes the luminance lookup table more correct, although the
visual difference is relatively small.
- speedup of inner loop, using dst[i] instead of *dst++
based on patch by Linards Ticmanis <ticmanis@coli.uni-sb.de>
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@8350 b3059339-0415-0410-9bf9-f77b7e298cf2