resolve.c: fix valgrind 'uninitialized memory' warning

fix the following warning generated by valgrind if ipv6 is enabled:

Syscall param write(buf) points to uninitialised byte(s)
   at 0x4000982: (within /lib/ld-2.9.so)
   by 0x80681A8: Resolve_Name (resolve.c:477)
   by 0x805439F: Conn_Handler (conn.c:1658)
   by 0x804AA7C: main (ngircd.c:331)

The warning is because ng_ipaddr_t can be a union, and only the
necessary parts are initialised.  The callers know what part
of the union is valid, so this is not a bug.

src/ngircd/resolve.c

@@ -291,6 +291,8 @@ ForwardLookup(const char *hostname, array *IpAddr)
 	if (!Conf_ConnectIPv4)
 		hints.ai_family = AF_INET6;
 #endif
+	memset(&addr, 0, sizeof(addr));
+
 	res = getaddrinfo(hostname, NULL, &hints, &ai_results);
 	switch (res) {
 	case 0:	break;