Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

General further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.

As python3 does not have raw_input(), convert it to input() when we
are using python3.

PR: 177214
Reviewed by: gnn
Approved by: sbruno (mentor)

Covert to python 3

Approved by: cperciva
MFC after: 3 days

Add SOFT as a possible section to exclude from counter list.

Add a reasonable error message telling the caller to specify a program
to be executed under hwpmc. If there is no program to run then
exit.

Remove UCP from the list of counters

Add options for program (-p) and to turn off waiting (-w) which is now
on by default.

The default is to wait after each counter is tested. Since the prompt
would go to stdout you won't see it if you're redirecting the output
of the executed sub-program to /dev/null, so just press return to
continue or Ctrl-D to stop.

Add a rudimentary test to run through all the available counters on a
system and then execute a program with pmcstat in counting mode.

The program will verify that all counters fire and that the code neither
panics the system nor locks it up. This should be considered a first pass
conformance test for new sets of counters being added to hwpmc(4).