Bug#689107: w3c-linkchecker

[Nicholas Bamber]

Piuparts issues have turned up for real now.
http://piuparts.debian.org/sid/fail/w3c-linkchecker_4.81-5.log
I'm not clear how I missed this but the cause is clear enough from
reading the ucf man page. ucf --purge does not actually delete the file.
I'll need to remove /etc/w3c/  if it's empty. Really it looks like a
good idea to standardize the directory as well, but probably not now.