kern/155490: [sysctl][patch] Document some sys/vm sysctls

[eadler at FreeBSD.org]

Synopsis: [sysctl][patch] Document some sys/vm sysctls

Responsible-Changed-From-To: freebsd-bugs->eadler
Responsible-Changed-By: eadler
Responsible-Changed-When: Tue Dec 6 07:10:56 UTC 2011
Responsible-Changed-Why: 
I'll take it.

http://www.freebsd.org/cgi/query-pr.cgi?pr=155490