[pico-ceu] API for Serial ports

[fsantanna]

Same API used in ceu-arduino:

https://github.com/ceu-arduino/driver-usart/blob/master/usart.ceu

• Also needs to receive a port parameter.
• Note: When addressing ports larger than COM9 in Windows you will have to specify the port thusly: "COM10" becomes "\\.\COM10" See: http://support.microsoft.com/default.aspx?scid=kb;EN-US;q115831

[AnnyCaroline]

The link wasn't working. Instead, I use as base this one.