Revert r10892, it's wrong and no longer needed to prevent crashes

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@11127 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavformat/rmdec.c

@@ -380,7 +380,7 @@ static int get_num(ByteIOContext *pb, int *len)
 
     n = get_be16(pb);
     (*len)-=2;
-//    n &= 0x7FFF;
+    n &= 0x7FFF;
     if (n >= 0x4000) {
         return n - 0x4000;
     } else {