don't have to keep this number updated at N different places
throughout the doc tree.
Update 3 instances of "4,000" in the Handbook to use this new entity.
should speak for themselves. Using these will significantly improve
consistency through the doc tree. Right now--before most of the
documents use these--there are five or six different spellings of
"FreeBSD-STABLE", even in the same document! &os; was added for
completeness.
Approved by: -doc