Has it been that long?

Revamp for a more modern Python style in the 3.12 era:

• start adding type annotations to code.
• use pyproject.toml
• remove illegal escape sequences

BuildTree now builds trees iteratively rather than recursively. With this we can handle larger trees which are needed in the decompilers.

Revise README.rst for the above and go over spelling and grammar

Internally, more git branches have been created to support older Python.