Before, we'd give up on transmitting the RC5 power signal if a different
NEC signal was received.  This resulted in some cases where the green
LED would get stuck on with no code being transmitted.

Now that doesn't happen anymore because we just wait until no more NEC
codes are received, then send the RC5 power signal.  That is, the power
signal only needs to be seen once, then once the channel is clear we
transmit.