Release 6.3 on next monday

[Poul-Henning Kamp]

We decided today that the 2019-09-15 release will happen next monday
and be called 6.3.

It will *not* be a long-term-support ("LTS") release.

Effectively immediately, we are in code freeze as far as source
code, but welcome any contribution pertaining to documentation and
release engineering.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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FreeBSD committer       | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.