Add ATmega328P Xplained Mini board. The board is an official
development kit from MCHP based on the Arduino UNO, reduced
hardware, with a xplainedmini debugger and CDC ACM serial
converter.
Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>
The volatile utils might be useful elsewhere - at least in a second unit test.
Move them to sys to allow using them, but with appropriate warnings added.