merged changes from Issue020_ThrottleWarning

based on current (10.2.2014) next branch, includes all changes from old
ThrottleWarning branch.

Solves issue 020: Throttle warning if P1-P3 is selected as Thr source.
Adds Turnigy TransmitterFix option
code savings:
120 bytes without Transmitter fix
4 bytes but 1 more data if Transmitter Fix is activated.

Added make option TURNIGY_TRANSMITTER_FIX for this purpose
TURNIGY_TRANSMITTER_FIX = NO   is default
set to YES for new Turnigy9x transmitter which transmits even no pulses
are generated.

Be careful about the issue with Switch as source for Mixer!