MFC 222530:

MFC 222530:
Add a new option to toggle the display of the system idle process (per-CPU
idle threads).  The process is displayed by default (subject to whether or
not system processes are displayed) to preserve existing behavior.  The
system idle process can be hidden via the '-z' command line argument or the
'z' key while top is running.  When it is hidden, top more closely matches
the behavior of FreeBSD <= 4.x where idle time was not accounted to any
process.

git-svn-id: svn://svn.freebsd.org/base/stable/8@223095 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f