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

This is pre-requisite for having efficient implementation of str<->bytes
conversion, and having that efficient is required with unfortunare
str vs bytes dichotomy in Python3.