MFC r242139:

Add CPU percentage limit enforcement to RCTL.  The resouce name is "pcpu".
It was implemented by Rudolf Tomori during Google Summer of Code 2012.

MFC r242957:

Don't divide by zero.

MFC r243070:

Fix kassert that's not really valid for %CPU accounting.  The problem
here is race between decaying the resource usage in containers, and updating
per-process usage; basically, the former may cause per-container usage
to get smaller than per-process usage.

MFC r243088:

Improve KASSERT messages in racct, to make it clear which resource
caused the problem.

MFC r248298:

Accessing td_state requires thread lock to be held.

MFC r248300:

When throttling a process to enforce RACCT limits, do not use neither
PBDRY (which simply doesn't make any sense) nor PCATCH (which could
be used by a malicious process to work around the PCPU limit).
MFC r242140:

Add pcpu to the the rctl(8) manual page.
MFC r243849 by bdrewery@:

- Move EXAMPLES descriptions to before the actual command
- Add mdoc macros for EXAMPLES
MFC r249375 by joel@:

Minor spelling and grammar fixes.
MFC r243856 by joel@:

Remove superfluous paragraph macro.