. Added conn_close to struct connection.
0 = Keep-Alive, 1 = Connection: close
. Added keepalive_connection() for recycling connection structs.
. Made "Connection: close\r\n" in reply headers optional.
. If protocol is HTTP/1.1, use Keep-Alive, unless Connection: close is
given in the request.
Offtopic:
. Improved request parsing - allow extraneous spaces.