HEADS UP: Recompile milters after sendmail 8.14 upgrade

[Gregory Shapiro]

sendmail has been updated from version 8.13.8 to 8.14.1 in the HEAD and
RELENG_[456] branches.  This upgrade includes a new libmilter library
which requires all dynamically linked milters to be recompiled (no
source code changes are required).

Unfortunately, this problem (the need to recompile filters) was found
after the MFC.  The release engineering team has asked for this notice
instead of doing a full backout of sendmail 8.14 in the RELENG_[456]
branches.

I'm sorry for the adverse effects from the change and will be more
careful with future sendmail commits.