Implement RC fail-safe

flix/flix.ino

@@ -28,6 +28,7 @@ float dt; // time delta from previous step, s
 float loopFreq; // loop frequency, Hz
 int16_t channels[RC_CHANNELS]; // raw rc channels
 float controls[RC_CHANNELS]; // normalized controls in range [-1..1] ([0..1] for throttle)
+float controlsTime; // time of the last controls update
 Vector gyro; // gyroscope data
 Vector acc; // accelerometer data, m/s/s
 Vector rates; // filtered angular rates, rad/s