the sy_download is finish implementing, but still some problems...

[uniray7]

1. I use uv_thread instead of uv_queue to run uv_fs_download(). If using uv_queue, it will core dump.
2. the rtcdc cannot be terminate, the librtcdc is not finished implementing.
3. the file_server is not stable. whenever the file_server serve over 3 download request from 3 client, the file_server may crash
   (*** Error in `./file_server': malloc(): memory corruption (fast): 0x00000000008e0690 *** )
   Segmentation fault (core dumped)

update: this problem3 is solve, the reason is setting wrong size when memory allocate