Circular header dependencies

[adbancroft]

The header files for most fakes include ArduinoFake.h, which results in circular header dependencies. E.g. EEPROMFake.h -> ArduinoFake.h -> EEPROMFake.h

This can result in compiler errors for the host program due to #pragma once. E.g. #include <Print.h> -> PrintFake.h -> ArduinoFake.h -> PrintFake.h

[adbancroft]

I have a branch that fixes this, but need #74 & #72 accepted first.