#288 Non-standard baudrates on Linux

[Jacek Ozimek]

Motorola GM300 communicates with serial adapter at 952bps and 7680bps with GM300 service program, which is commonly run using DOSBox. This baudrate works with specific adapters on Windows but on Linux requesting non-standard baudrates causes problems.

Here tests have been gathered:
https://docs.google.com/document/d/19rn-9F8jEXGQh0jJ9RjlResgmjxTvCNhy4t7qWnsfJ8/edit?usp=sharing

I was not able to test it on MACOS so far, but I haven't split LINUX and MACOS implementation in attached diff for keeping a clearness.