fix for non ansi serial baud rates on linux (e.g. solidoodle 2: 250000)

This fixes https://github.com/repetier/Repetier-Host/issues/156 without the need to compile Mono yourself, but needs Python on the system.

Mono on Linux cannot open serial ports on non-ansi baud rates, like the 250000bps needed for communication with e.g. Solidoodle 2.
This is described in multiple bug reports against Mono, even with a patch attached and has no been fixed in years as mentioned here:
http://stackoverflow.com/questions/13206524/error-with-high-baud-rates-using-serialport-on-mono-linux
So this workaround uses Python to set the correct baud rate on systems using Mono, which should work on most Linux and OSX system since they usually have Python installed...