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.

motor.c

@@ -4,6 +4,7 @@
 #include "timer.h"
 #include "dcm.h"
 #include "uart.h"
+#include "status.h"
 
 float integral[3] = {0.0f, 0.0f, 0.0f};
 float last[3];
@@ -69,7 +70,7 @@ void motor_pid_update(float troll, float mroll,
 	out[1] = pitch * Kp   + integral[1] * Ki   + derivative[1] * Kd;
 	out[2] = yaw   * Kp_y + integral[2] * Ki_y + derivative[2] * Kd_y;
 
-	if (armed) {
+	if (status_armed()) {
 		/* Front right */
 		motor[0] = throttle + out[0] + out[1] + out[2];
 		/* Front left */
@@ -147,7 +148,7 @@ void motor_kill(void) {
 }
 
 void motor_set_throttle(float t) {
-	if (armed)
+	if (status_armed())
 		throttle = t;
 }