Add code to reflect USB ACM parity setting to the passthrough port alongside existing support for ACM baud rate changes. Some use cases for serial passthrough require specific parity settings.
For example, even parity is used and required by the USART protocol used in the STM32 system bootloader. This enhancement allows the use of standard flash programming tools such as STM32CubeProgrammer to flash connected STM based peripherals such as Receivers and Telemetry radios via serial passthrough. Some examples of such peripherals include the FrSky R9 receivers as well as various other STM based LoRa modules used by the mLRS project.
termios2 not available on cygwin. This needs a re-think for cygwin. For now let's just hide it by letting it be declared empty by the virtual and totally bypass it in the cygwin build.
Richard Allen
Brad Bosch
Patrick José Pereira
Pierre Kancir
Andrew Tridgell
Siddharth Purohit
Tom Pittenger
Mark Whitehorn