A very, *very* poor-man's version of label<->address dump.  Ugh!
Rework label map collection

This uses a pass to interrogate the system for locations, then dumps
those out instead. It handles includes, anonymous labels, and basic
macros, but it does so in a somewhat ugly way. This data can be
readily abbreviated and should also be re-sorted.
Much prettier label map files
Refactor the label mapper to be more like the lister.