Checkpointing my current changes to xcvb.

Beware: this revision is WHOLLY UNTESTED. Not even compiled.
You may want to check out the revision tagged xcvb_0.1
to get the last reported working version as written by Spencer Brody.

Changes include:
* An update to the existing documentation.
* An attempt at recognizing and skipping comment headers to modules
* Trying to split essential run-time code into a "driver" file.
* Adding a "macros" file, refactoring utilities,
* refactoring the xcvb graph traversal.
* Some superficial changes (whitespace, function names, documentation)