Allow cwm(1) to cycle through windows of the same window class as the

active window; default key binding to M-grave, respectively Alt-Tilde,
like other window managers have as well.

from Simon Dassow

calmwm.h

@@ -67,6 +67,7 @@
 #define CWM_CYCLE_FORWARD	0x0001
 #define CWM_CYCLE_REVERSE	0x0002
 #define CWM_CYCLE_INGROUP	0x0004
+#define CWM_CYCLE_INCLASS	0x0008
 
 enum cwm_status {
 	CWM_QUIT,