daemon: parse_host_and_port SIGSEGV if port is specified

This typo will lead to git-daemon dying any time the connect
string includes a port after the host= attribute. This can lead
for example to one of the following error messages on the client
side when someone tries git clone git://...:<port>.

When the daemon is running on localhost:
  fatal: The remote end hung up unexpectedly

or when the daemon is connected through an ssh tunnel:
  fatal: protocol error: bad line length character: erro

In the latter case 'erro' comes from the daemon's reply:
  error: git-daemon died of signal 11
Signed-off-by: NImre Deak <imre.deak@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

daemon.c

@@ -420,7 +420,7 @@ static void parse_host_and_port(char *hostport, char **host,
 		*host = hostport;
 		*port = strrchr(hostport, ':');
 		if (*port) {
-			*port = '\0';
+			**port = '\0';
 			++*port;
 		}
 	}