campaignd: Tiny variable refactoring
campaignd: Quick-and-dirty implementation of upload-time blacklisting

A path to a blacklist WML file may be provided in the campaignd
configuration file (server.cfg). The BL file, in turn, may contain
attributes for comma-delimited lists of wildcard patterns, accepting
shell-style '*' and '?', by leveraging utils::wildcard_string_match()'s
functionality.

The following lists of patterns are recognized at this time:

  ip=<numeric IPv4 address masks>
  email=<add-on author email masks>
  name=<add-on id/name masks>
  title=<add-on title masks>
  author=<add-on author masks>
  description=<add-on description masks>

Currently, the IP address mask list also takes '*' and '?' wildcards. My
intention is to use CIDR subnet masks instead of or in addition to this.

The blacklist WML file is only read by campaignd once at startup and
it's never written to, thus allowing to preserve any WML comment lines
that may be included in the file by admins for convenience.

The IP, email, name, title, author, and description of a (new or
existing) uploaded add-on are matched against the blacklist in that
order. If the add-on matches, the upload is aborted and the user is
shown a generic message in English, just like with every other possible
campaignd-side error (on the plus side, this means it can be backported
to 1.12).

All matches (except for IP matches, which only contain digits and
punctuation) are done case-insensitively.

Because of campaignd protocol limitations, the upload is only checked
and aborted after the client has already uploaded a weighty WML document
including the add-on archive. Such is life, I guess.
campaignd: Forgot to add a Doxygen comment to the last commit
Add test cases for utils::wildcard_string_match()
Test a few counterintuitive wildcard_string_match() border cases

It's probably best to leave them alone for now, though.
campaignd: Remove dead code
Merge branch 'backport/1.12/campaignd-blacklist' into 1.12