add MMX and SSE versions of ff_snow_inner_add_yblock

Patch by Robert Edele < yartrebo AH earthlink POIS net >
Original Thread:
Date: Mar 22, 2006 3:24 AM
Subject: [Ffmpeg-devel] [PATCH] snow mmx + sse2 part 5

Originally committed as revision 5197 to svn://svn.ffmpeg.org/ffmpeg/trunk