GTRUVIN9XPCB: DSM2=PPM mode -- Implemented hardware switching of PPM_OUT pin

and compensated for main clock synchronisation to get accurate 8us bit 
lengths, as measured on the logic analsyser. 

Specifically, all 1 and 0 bits now measure 8.000us in length, instead of 
varyting from 6.250us to 10.750us, as before.

NOTE: A similar len-5 / len+3 compensation is almost certainly required
      to improve bit timing on the stock board, in software bit-bang mode,
      but I did not want to commit such a change to trunk without being
      able to bench test it first. The values might differ slightly, due
      to the number of instruction cycles executed before the actual
      PORT B bit toggle code is reached. But it will NOT be the same for 
      both 1 and 0 bits.

src/Makefile

@@ -183,6 +183,7 @@ EXTRA_ROTARY_ENCODERS = NO
 # On G9X V4 board, when VOICE=NO:
 #  PORTH:7 --> Transistion LOW to HIGH = start of setupPulses(). Transistion HIGH to LOW = end of setupPulses().
 #  PORTH:6 --> LOW->HIGH = start of mixer calcs. HIGH->LOW, end of mixer calcs.
+# Values = YES, NO
 DEBUG = NO
 
 # Flight Phases