Log Message:
Updated to version 3.1.8.

Pkgsrc changes:
  - some cleanup of the Makefile to shut up a few pkglint notes and warnings
    (USE_TOOLS, SUBST_CLASSES).

Changes since version 3.1.7:
============================
3.1.8 is a major bug-fix release, including a potential DoS.  The major
highlights are:

- bug 5318: fix for CVE-2007-0451: possible DoS due to incredibly
  long URIs found in the message content.
- bug 5240: disable perl module usage in update channels unless
  --allowplugins is specified
- bug 5288: files with names starting/ending in whitespace weren't usable
- bug 5056: remove Text::Wrap related code due to upstream issues
- bug 5145: update spamassassin and sa-learn to better deal with STDIN
- bug 5140 and 5179: improvements and bug fixes related to DomainKeys
  and DKIM support
- several updates for Received header parsing
- several documentation updates and random taint-variable related issues