clamav update in wip

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

Hello
I commited a clamav update to 1.4.3 to wip.
For now I only checked that freshclam can download signatures and
clamd can start. I will test on a real mail server in the next few days.

clamav now uses cmake and rust/cargo, please review my changes for
common mistakes with these tools. Also, I didn't work on options.mk yet.
If you're using clamav with libmilter you're welcome to work on it :)

Also, testing the build on something else than netbsd-10/amd64 is welcome.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
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