Make type inference compatible with Python 3.6

Starting in Python 3.6, instructions always use two bytes. As the Python SDKs implementation of trivial type inference relies on these disassembled instructions, typehints/trivial_inference.py should be updated to be compatible with this change. This can be done by comparing https://github.com/python/cpython/blob/3.6/Lib/dis.py to https://github.com/python/cpython/blob/3.5/Lib/dis.py