kern/148510: [sysctl][patch] Document some sysctls

[vwe at FreeBSD.org]

Synopsis: [sysctl][patch] Document some sysctls

State-Changed-From-To: open->analyzed
State-Changed-By: vwe
State-Changed-When: Sun Aug 15 22:45:05 UTC 2010
State-Changed-Why: 
patch applies well
for the committer taking this (that was a HINT!;), please also take a look at kern/148710

http://www.freebsd.org/cgi/query-pr.cgi?pr=148510