Improve handling of arming, providing LED blink codes if the arming fails.

Also, implement a software watchdog to make sure that the main real-time
modules are actually being run. Provide a panic facility, also giving blink
codes to indicate the panic reason.

led.c

@@ -11,13 +11,14 @@ unsigned int led_next_time;
 bool led_next_state;
 
 led_pattern led_pattern_active[] = {250, 250, 0};
+led_pattern led_pattern_unknown[] = {100, 100, 0};
 
 void led_set(bool on)
 {
 	if (on)
-		FP0XVAL |= 0x04000000;
-	else
 		FP0XVAL &= ~0x04000000;
+	else
+		FP0XVAL |= 0x04000000;
 }
 
 void led_update(void)
@@ -43,8 +44,15 @@ void led_update(void)
 
 void led_set_pattern(led_pattern *pattern)
 {
+	if (led_current_pattern == pattern)
+		return;
 	led_current_pattern = pattern;
-	led_current_pointer = pattern;
+}
+
+void led_init(void)
+{
+	led_current_pattern = led_pattern_unknown;
+	led_current_pointer = led_pattern_unknown;
 	led_next_state = TRUE;
 	led_next_time = timer_read();
 	led_update();