Minor optimization for sse2 yuvj conversion.
Minor optimization for sse2 yuvj conversion.

svn path=/trunk/libavg/; revision=5099

libavg/libavg,scotty007/libavg,yyd01245/libavg,th3infinity/libavg,hoodie/libavg,hoodie/libavg,scotty007/libavg,th3infinity/libavg,scotty007/libavg,hoodie/libavg,yyd01245/libavg,libavg/libavg,th3infinity/libavg,scotty007/libavg,yyd01245/libavg,libavg/libavg,hoodie/libavg,libavg/libavg,yyd01245/libavg,th3infinity/libavg