1. Add the new method mkd_string(), which assembles a list from a string.
2. Add a tests directory and three test files.
3. Move the smartypants code out into a separate function, so I can
(eventually) pass a /don't_be_clever/ flag in to the markdown()
function.
4. Redo the mail address mangler so I can mangle the
mailto: as well as the address.
5. Fix a bug in the DELETE() macro in cstring.h
6. Fix dependencies in the Makefile so that a reconfigure forces a
complete recompile.
7. Code tweaks to make gcc stfu
8. Tweak the build dependencies again.
