Fix recent changes to not break non-IPV6-aware systems.

src/backend/libpq/hba.c

@@ -548,6 +548,8 @@ ipv4eq(struct sockaddr_in *a, struct sockaddr_in *b)
 	return (a->sin_addr.s_addr == b->sin_addr.s_addr);
 }
 
+#ifdef HAVE_IPV6
+
 static bool
 ipv6eq(struct sockaddr_in6 *a, struct sockaddr_in6 *b)
 {
@@ -560,6 +562,8 @@ ipv6eq(struct sockaddr_in6 *a, struct sockaddr_in6 *b)
 	return true;
 }
 
+#endif /* HAVE_IPV6 */
+
 /*
  * Check to see if a connecting IP matches a given host name.
  */
@@ -614,6 +618,7 @@ check_hostname(hbaPort *port, const char *hostname)
 					break;
 				}
 			}
+#ifdef HAVE_IPV6
 			else if (gai->ai_addr->sa_family == AF_INET6)
 			{
 				if (ipv6eq((struct sockaddr_in6 *) gai->ai_addr,
@@ -623,6 +628,7 @@ check_hostname(hbaPort *port, const char *hostname)
 					break;
 				}
 			}
+#endif
 		}
 	}