Updating PPS code to reflect bug fixes in XC16-1.21 compiler.
Switched interrupt declarations to use _ISR macro.
This adds a compilation warning about a missing auto_psv attribute, but it makes this code more compatible with other PICs.
Various UART1 lib fixes:
 * Added a check in Uart1TX interrupt to make sure the last character was transmit before continuing the interrupt.
 * Altered Uart1Init(...) so that it should be suitable for re-initializing the interrupt.
Fixed warning about pointer being used improperly in Ecan1 lib.
Fixed PrimaryNode.c to work on XC16 1.21.
PPS and ADC macros in Microchip's peripheral lib changed.
Also compiler warning fix.
MavlinkObserver code now triggers a digital output pin when a MAVLink corruption is detected.