Add 'getidle' CPU utilization measurement infrastructure

kernel/clock.c

@@ -118,6 +118,8 @@ PUBLIC int bsp_timer_int_handler(void)
 {
 	unsigned ticks;
 
+	IDLE_STOP;
+
 	if(minix_panicing)
 		return 0;
 
@@ -228,6 +230,8 @@ PUBLIC int ap_timer_int_handler(void)
 	int expired = 0;
 	struct proc * p, * billp;
 
+	IDLE_STOP;
+
 	/* Update user and system accounting times. Charge the current process
 	 * for user time. If the current process is not billable, that is, if a
 	 * non-user process is running, charge the billable process for system