Refactor the src/dirtree.c file into smaller chunks, one for the pr_conf_*
API, and keeping the rest, for now.  This makes it possible to a) write unit
tests for that API, and b) write unit tests for other APIs (such as the Auth
API) by reducing complexity of the unit test build/link.
Merge pull request #10 from proftpd/dirtree-refactoring

Refactor the src/dirtree.c file into smaller chunks, one for the pr_conf...