Mp4: fix seeks after the last key frame. Mp4 module does not allow seeks after the last key frame. Since stss atom only contains key frames it's usually shorter than other track atoms. That leads to stss seek error when seek position is close to the end of file. The fix outputs empty stss frame instead of generating error.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


cat << END >> $NGX_AUTO_CONFIG_H

#ifndef $have
#define $have  0
#endif

END