Simplify key/mb binding moving argtype into flags and dropping another

variable; removes the need to zero out struct binding, leaving a simple
malloc.

calmwm.h

@@ -84,6 +84,7 @@
 #define CWM_NOGAP		0x0002
 
 #define CWM_WIN			0x0001
+#define CWM_CMD			0x0002
 
 #define CWM_QUIT		0x0000
 #define CWM_RUNNING		0x0001
@@ -252,7 +253,6 @@ struct binding {
 	unsigned int		 modmask;
 	union press		 press;
 	int			 flags;
-	int			 argtype;
 };
 TAILQ_HEAD(keybinding_q, binding);
 TAILQ_HEAD(mousebinding_q, binding);