Includes replacing flight_mode_strings with print_flight_mode function.
SendDebug macro replaced with direct Serial.print_P calls.

Channel count auto detection post processing code
Added a #define : valid frames threshold before detection validation

Particularly important is the roll-pitch I term move from the stabilize to rate controllers.

#define Stupid_Mistake

SPI3: add checks that SPI bus has been initialised to reduce possibility of interfering with UART3 on APM1

SPI3 is also UART3.  On APM1 we use UART3 for telemetry and don't need SPI3.

AP_OpticalFlow: added ability to pass in semaphores for main spi bus to stop conflicts with dataflash on APM1

DataFlash_APM2: renamed semaphore to spi3_semaphore to make it more obvious which semaphore is required.

this sends out the GPS init strings in 16 byte chunks to avoid causing
timing glitches when no GPS is attached

Reworked the PPM decoder (i did forget the sync symbol pre-pulse)
Splitted pre-pulse and pulse width variable for better reliability and easier processing

Also removed commented-out block of code from navigation.pde.

Provided by Leonard Hall.

Also removed large unnecessary comments.

Provided by Leonard Hall