VC1: use memmove instead of memcpy on overlapping memory

(cherry picked from commit 234d20686d2fe81ff2f631b60b5457e507e583b1)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/packetizer/vc1.c

@@ -168,7 +168,7 @@ static int Open( vlc_object_t *p_this )
         /* With (some) ASF the first byte has to be stripped */
         if( p_extra[0] != 0x00 )
         {
-            memcpy( &p_extra[0], &p_extra[1], p_dec->fmt_out.i_extra - 1 );
+            memmove( &p_extra[0], &p_extra[1], p_dec->fmt_out.i_extra - 1 );
             p_dec->fmt_out.i_extra--;
         }