Currently TERM is checked for every message. Could be memoized, but it
would add complexity, and typical propellor output is not going to be more
than a few hundred messages, and likely this will be swamped by the actual
work.
This is to work around OSX's brain-damange regarding filename case
insensitivity.
Avoided moving config.hs, because it's a config file. Put in a symlink to
make build work.