- Add support for dumping current resource usage for processes via a new -r
  flag to procstat.
- Add an -H flag to request information about threads rather than processes
  when dumping statistics.  Currently it is only used for -r to display
  resource usage for individual threads instead of the entire process.

Reviewed by:	kib (older version without -H)
MFC after:	1 month
Correct some minor nits in the per-thread signal format description such
as missing posessives and misordering of fields.

MFC after:	1 week