[core] fix build --disable-ipv6 (fixes #2832)

x-ref:
  "Build error on systems without IPV6 support (regression from 1.4.46)"
  https://redmine.lighttpd.net/issues/2832

github: closes #87

src/network.c

@@ -77,9 +77,13 @@ static void network_host_normalize_addr_str(buffer *host, sock_addr *addr) {
     if (addr->plain.sa_family == AF_INET6)
         buffer_append_string_len(host, CONST_STR_LEN("]"));
     if (addr->plain.sa_family != AF_UNIX) {
+      #ifdef HAVE_IPV6
         unsigned short port = (addr->plain.sa_family == AF_INET)
           ? ntohs(addr->ipv4.sin_port)
           : ntohs(addr->ipv6.sin6_port);
+      #else
+        unsigned short port = ntohs(addr->ipv4.sin_port);
+      #endif
         buffer_append_string_len(host, CONST_STR_LEN(":"));
         buffer_append_int(host, (int)port);
     }