Contrib: UPNP: enable IPv6 and re-enable webserver (broken in 1.6.17).

With disabled webserver, linking fails at least on OSX and Linux, see
http://forum.videolan.org/viewtopic.php?f=12&t=101229 f.i.

contrib/src/upnp/rules.mak

@@ -28,6 +28,6 @@ endif
 ifdef HAVE_WIN32
 	$(RECONF)
 endif
-	cd $< && $(HOSTVARS) CFLAGS="$(CFLAGS) -O3 -DUPNP_STATIC_LIB $(LIBUPNP_ECFLAGS)" ./configure --disable-samples --without-documentation --disable-webserver $(HOSTCONF)
+	cd $< && $(HOSTVARS) CFLAGS="$(CFLAGS) -O3 -DUPNP_STATIC_LIB $(LIBUPNP_ECFLAGS)" ./configure --disable-samples --without-documentation --enable-ipv6 $(HOSTCONF)
 	cd $< && $(MAKE) install
 	touch $@