[Exim] bug: ACLs in files

My ACLs were growing to half the size of my 1000-line configuration file,
so I thought I'd break them out into separate files (yes, there's a slight
performance penalty, but it's insignificant compared to virus-scanning)
for manageability.

Unfortunately ACLs in files are not allowed to have comments :-( so it's
back to one big file for me for now. I guess the fix is pretty easy, but
regrettably I've been rather busy all term.

Matt