As part of this, rejig the way TIM3 is initialised, since it's now
shared by USB CDC and the blue LED PWM.

Fixed some math functions and added more exceptions.

Fixed some math functions and added more exceptions.

objgenerator: Implement exception handling for generators

Fixed modulo operator on ints and mp ints to agree with python. Added intdivmod.c and tests/basics/modulo.py.

This is required to properly handle exceptions across yields.

Added exception hierarchy except for OSError and UnicodeError (requires arguments). Comment out the errors that aren't needed if memory becomes an issue.

This gives a functioning, independent MSC device.

Make str and bytes be proper types