- Update OpenSMTPD extras to 6.6.0 release
- Drop deprecated upstream filters and tools

mail/opensmtpd-extras-filter-monkey: Spell PORTEPOCH correctly

Since it was misspelled PORTEPOCH=1 was inherited from opensmtpd-extras.
There is no going back now.

- Update OpenSMTPd to 6.6.0 portable release
    This release builds with LibreSSL > 3.0.2 or OpenSSL > 1.1.0.
    FreeBSD 11.x users should update to 12.x/13.x or switch system-wide
    default ssl library to openssl111/libressl

- Update -extras to 6.4.0 release
    Filters still missing, corresponded ports temporary markes
    as IGNORED

PR:		213442,228937
MFH:		2019Q4

devel/libevent2: drop historical suffix after r362796

PR:		216777
Approved by:	mm (maintainer)

devel/libevent2: update to 2.1.8 and cleanup

- DEFAULT_VERSIONS += ssl=openssl-devel is now supported
- devel/py-event and devel/p5-Event-Lib are marked BROKEN

Changes:	https://github.com/libevent/libevent/raw/release-2.1.8-stable/whatsnew-2.1.txt
Changes:	https://github.com/libevent/libevent/raw/release-2.1.8-stable/ChangeLog
PR:		216527
Exp-run by:	antoine
Approved by:	mm (maintainer)

- Update OpenSMTPD-extras to 201606230001 snapshot
- Consolidate all -extras under one maintainership

NOTE:	Author still warning everyone about experimental status of filters.
	All --with-filter-XXX replaced with --with-experimental-filter-XXX

Approved by:	adamw

Install missing ready-to-use OpenSMTPD-extras components:

- filter-monkey
- table-ldap
- tools-stats

Also install experimental components (corresponding groups labelled as
"experimental"):

- filter bindings to lua, perl and python languages
- queue and scheduler bindings to perl and python languages

Submitted by:	myself
Reviewed by:	gahr, adamw, miwi
Approved by:	gahr, adamw, miwi (mentor, implicit)
Sponsored by:	milk and cookies
Differential Revision:	https://reviews.freebsd.org/D6084