Add a Python script to replace C identifiers and generate commit messages

I sometimes want to replace identifiers in the source code. When I do that, I wind up writing a little perl script, then a shell script to apply that perl script to all the code, and then I write a commit message. But if I'm feeling lazy, I might skip a step, or mix other stuff in with the automated commit. That's not so great.

I've got a script to automate this process.