FreeBSD malloc aligns on 16 byte boundaries, so no need to use memalignhack.

patch by Dennis Melentyev, dennis ##dot## melentyev ##at ## gmail ##dot## com

Originally committed as revision 6005 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1236,7 +1236,8 @@ if check_header malloc.h; then
 fi
 
 if test "$_memalign" = "no" -a "$mmx" = "yes" -a \
-        "$memalignhack" != "yes" -a "$targetos" != "Darwin" ; then
+        "$memalignhack" != "yes" -a "$targetos" != "Darwin" -a \
+        "$targetos" != "FreeBSD" ; then
     die "Error, no memalign() but SSE enabled, disable it or use --enable-memalign-hack."
 fi