This allows the mailbox to be used for Serial (instead of polling shared
memory). The CurieMailbox library, in the codk-m-corelibs branch, will
not require any API changes, but will now just be a thin wrapper around
the methods in mailbox.cpp

-set pinMode for RX and TX pins inside of begin instead of the
constructor

-move the Power Management library from
https://github.com/bigdinotech/Arduino101Power

-use the IPM instead of shared memory for passing data between ARC
and x86 cores for cdc-acm.

The Arduino IDE requires the use of a tab separator between the name and identifier. Without this tab the keyword is not highlighted.

Reference: https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification#keywords

-set a baud rate limit for cdc-acm due to the limitation of Inter Processor Mailbox

This is part of a move to encourage use of the standard bool type over Arduino's non-standard boolean type alias.

According to arduino/Arduino#6395, these delays are required for the SPI communication with the digital potentiometer to work.

Replace boolean type with bool in examples

Add necessary delays to SPI DigitalPotControl example