psql: Show IP address in \conninfo

When hostaddr is given, the actual IP address that psql is connected to
can be totally unexpected for the given host.  The more verbose output
we now generate makes things clearer.  Since the "host" and "hostaddr"
parts of the conninfo could come from different sources (say, one of
them is in the service specification or a URI-style conninfo and the
other is not), this is not as silly as it may first appear.  This is
also definitely useful if the hostname resolves to multiple addresses.

Author: Fabien Coelho
Reviewed-by: Pavel Stehule, Arthur Zakirov
Discussion: https://postgr.es/m/alpine.DEB.2.21.1810261532380.27686@lancre
	https://postgr.es/m/alpine.DEB.2.21.1808201323020.13832@lancre

src/interfaces/libpq/libpq-int.h

@@ -397,6 +397,7 @@ struct pg_conn
 	int			nconnhost;		/* # of hosts named in conn string */
 	int			whichhost;		/* host we're currently trying/connected to */
 	pg_conn_host *connhost;		/* details about each named host */
+	char	   *connip;			/* IP address for current network connection */
 
 	/* Connection data */
 	pgsocket	sock;			/* FD for socket, PGINVALID_SOCKET if