unconciousness -> unconsciousness; from snj@netbsd, -r1.5

use .Mt for email addresses; from Jan Stary <hans at stare dot cz>; ok jmc@

within Rs/Re reference blocks, use %U instead of %O (or any other
variants) for URLs, allowing mandoc -Thtml to properly generate links;

(sendmail.8 changes are simply using Lk, which i somehow miss

within Rs/Re reference blocks, use %U instead of %O (or any other
variants) for URLs, allowing mandoc -Thtml to properly generate links;

(sendmail.8 changes are simply using Lk, which i somehow missed in previous)

ingo reminded me to verify that gnu groff recognises %U: 1.20.1 does not,
but 1.21 does;

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tweak previous;

rename uyurex(4) to utwitch(4).

ok deraadt@