A faster Python difflib

As part of a push for making it easier to develop faster and more readable core/stdlib code for the CPython runtime, I have written a short patch against the difflib module in the Python standard library to make it a) compile with Cython and b) run faster as a compiled binary module. The net result is that it runs more than 50% faster with only the minor code modifications provided in the patch, and still about as fast in the normal CPython interpreter.