re-worded and ok djm

Register information from NetBSD (except for KA53), logic from OpenBSD/sparc.

Note:
While testing the new option, we noticed that our stable tftpd has
a problem if any option is set (e.g. tsize) and you try to put a file.
This has nothing todo with our new blksize option.  We fix this as
next.
ok claudio@

into mobile. discussed with and spelling by jmc@

ok henning

By Steven G. Kargl <kargl at troutmask dot apl dot washington.edu>
From FreeBSD

SpamHaus no longer publish their SBL in a free, downloadable form
suitable for use with spamd. They obviously care more about
subscription dollars than really fighting spam - very sad.
ok deraadt@

OK deraadt@

dot org>; ok djm@ deraadt@

david@; ok henning@

fix as proposed by maja@, thanks!

a few frequency adjustments. ok henning@

up causes overcompensation and confusing debug log entries; noticed
by dtucker@

henning@

ok henning@ ckuethe@

more than one token MUST be put in parentheses!

only do frequency compensation if the clock is synced, and a slightly
diffent way of computing the linear regression.
You'll need a recent kernel and libc to use this.
Testing by naddy@ and ckuethe@ and others, thanks!
ok henning@

marked obsolete since the opendev() behaviour it turned on is now the
default.
'it can go' deraadt@
'no API of mine has ever made it into a standard' downsj@

ok todd

ok henning@

overcompensating. From DragonFly, uses recent adjtime(2) changes,
so you'll need a recent kernel. ok henning@

descriptive while at it, input and okay jmc@

ok henning@

ok deraadt@ cloder@