Implement _NET_VIRTUAL_ROOTS (just clear it, we don't use that technique)

and _NET_SHOWING_DESKTOP (we're never doing so right now).

only three informational root-window hints to go.

ok okan@

calmwm.h

@@ -536,7 +536,9 @@ extern struct conf			 Conf;
 #define	_NET_CURRENT_DESKTOP		 cwm_atoms[13]
 #define	_NET_DESKTOP_VIEWPORT		 cwm_atoms[14]
 #define	_NET_DESKTOP_GEOMETRY		 cwm_atoms[15]
-#define CWM_NO_ATOMS			 16
+#define	_NET_VIRTUAL_ROOTS		 cwm_atoms[16]
+#define	_NET_SHOWING_DESKTOP		 cwm_atoms[17]
+#define CWM_NO_ATOMS			 18
 #define CWM_NETWM_START			 7
 
 extern Atom				 cwm_atoms[CWM_NO_ATOMS];