Bug fix:
========
Fixed another possible core dumps on verify.


Minor feature changes:
======================
Recognize base64-encoded MLM footers.
The "whitelisted" comment in Authentication-Results:
set sparingly (see whitelisted_pass below).


Documentation:
==============
zdkimfilter.conf(5) whitelisted_pass,
zdkimverify(1) -o option, and
zdkimfilter(8) --save-files.
