#180 Allow setmode(GPIO.BOARD) to be forced

[Paul Grimes]

I am using a Raspberry Pi CM3+ compute module in a Waveshare PoE I/O board that recreates the RPi 40 pin header on the board, so that standard HATs etc, can be used with the CM3/CM3+. If I could force RPi.GPIO.setmode() to accept GPIO.BOARD on the CM3+, I could avoid changing a significant amount of other code.

Could a keyword argument be added to .setmode() to allow the user to override the error checking for Raspberry Pi type?