Some experimental Python macros to hopefully simply Python packaging.

Also contains a quick rewrite of spectool in python which will handle Source: lines containing arbitrary macros.

The spectool rewrite is currently feature-complete. It should accept the same inputs and produce the same output and return codes as the original. At this point any differences (except in help or debug output) for general use cases should be considered bugs.

Ideas:

• Don't do anything at all for existing specs. If they work, they shouldn't need to change.
• Provide convenience macros wherever it is reasonable to provide them.
• Try to make the resulting spec look both clean and readable.
• Where define what's essentially new syntax, try to make it look like existing syntax.