Support sending BREAK character

[yodaldevoid]

When interfacing with some systems, namely Linux systems using agetty, over serial the BREAK character is used to force the baud rate to change. Currently I don't see a way to send a BREAK character using SimplySerial.

[yodaldevoid]

A note for anyone looking to implement this, the BREAK state can be set using SerialPort.BreakState. A quick timer will need to be used to make sure the BREAK state is asserted for long enough before being cleared.