switched spm_srxl.c to C++ compilation
Correctly set budget for half-duplex writes
Tidy PACKED and other externalities
disable SRXL2 on IOMCU and softserial - SRXL2 is a serial half-duplex protocol-only
fixed buffer overrun in SRXL2 parser
fix bugs in decoder sketch and allow output to SITL
Andy Piper