[Exim] Snapshot available for testing maildirsize

I have put a snapshot of the current source tree in

ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/Testing/exim-snapshot.tar.gz
ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/Testing/exim-snapshot.tar.gz.sig

This contains the re-written code for maildirsize support, as discussed
previously. In particular:

    . If the quota is zero, the maildirsize file is maintained, but no quota is
      imposed.

    . If the maildir directory does not exist, it is created before any attempt
      to write a maildirsize file.

    . The quota value in the file is just a cache; if the quota is changed in
      the transport, the new value overrides.

    . A regular expression is available for excluding directories from the
      count. This is set by the maildir_quota_directory_regex option, whose
      default value is

        maildir_quota_directory_regex = ^(?:cur|new|\..*)$

      which includes the cur and new directories, and any maildir++ folders,
      which are directories whose names begin with a dot. If you want to
      exclude the Trash folder from the count (as some sites do), you need to
      change this setting to

        maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$

      which uses a negative lookahead in the regex to exclude the directory
      whose name is .Trash. This option (maildir_quota_directory_regex) is used
      only when maildir_use_size_file is set.

I believe I have implemented the "rules" that are documented in
http://www.inter7.com/courierimap/README.maildirquota.html
reasonably closely. The idea is to improve compatibility with other
software that supports this.

If you are keen on using maildirsize, please test this snapshot and give
me feedback. Other changes to the code are documented in doc/ChangeLog.

Philip

--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.