introduce the beginnings of netwm support, minimally and correctly;

allows java to be happy, but additionally stops others from whinning
about a non-netwm complaint wm.  more to come.

written a few times; this one includes a clever hack from oga@ to
populate _NET_SUPPORTED.

ok oga@

calmwm.c

@@ -166,6 +166,8 @@ x_setupscreen(struct screen_ctx *sc, u_int which)
 	/* Initialize menu window. */
 	menu_init(sc);
 
+	xu_setwmname(sc);
+
 	/* Deal with existing clients. */
 	XQueryTree(X_Dpy, sc->rootwin, &w0, &w1, &wins, &nwins);