v3.9.0

6e84f2a connection: add api: close
2f951e5 send_head: use int64_t for content_length
81db1fa file: support handle large file
f2c55af file: fix bug: send "Content-Range" error
117ae81 src/uhttpd.c: fix build without dlopen
2f12b7d connection: New API: get_content_length
fa6248b uh_log_xx: check the arguments like printf
afeee7e Support set a callback for connection closed
6cf45fb uh_connection: Add a pointer to save context for user
971602f use url decode while handle file