MFC r318436:

usr.bin/getconf: add some initial tests

Items tested via this commit are:
- Some basic POSIX constants.
- Some valid programming environments with -v.
- Some invalid programming environments via -v.

NOTE: this test makes assumptions about ILP32/LP32 vs LP64 that are
currently not true on all architectures to avoid hardcoding some
architectures in the tests. I'm working on improving getconf(1) to be
more sane about handling ILP32/LP32 vs LP64. Future commits are coming
soon to address this.

Tested with: amd64, i386

MFC r318434:

Make the `.gperf.c` suffix rule depend on fake-gperf.awk

Parameterize out fake-gperf.awk to avoid duplicating the path

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Make this work under non-C locales.

PR: misc/45460
Approved by: re

Completely revamp the way getconf(1) works, for better adherence to the
intent of the Standard.

- Make getconf able to distinguish between configuration variables which
are entirely unknown and those which are merely not defined in the
compilation environment. The latter now get a more appropriate
"undefined\n" result rather than a diagnostic. This may not be
exactly right, but it's closer to the intent of the Standard than
the previous behavior.

- Support ``programming environments'' by validating that the environment
requested with the `-v' flag is the one-and-only execution environment.
(If more environments are supported for some platforms in the future,
multiple getconf(1) executables will be required, but a simple edit in
progenv.gperf will enable automatic support for it.) Document POSIX
standard programming environments.

- Add all of the 1003.1-2001 configuration variables. FreeBSD does not
support all of these (including some that are mandatory); getconf will
later be fixed to break the world should a required variable not be
defined.

As a result of all these changes, gperf is no longer adequate. Keep the
overall format and names of the files for now, to preserve revision history.
Use an awk script to process the .gperf files into C source, which does a
few things that gperf, as a more general tool, cannot do. The keyword
recognition function is no longer a perfect hash function.

This may obviate the need for gperf in the source tree.

- Add a small compile-time regression test to break the build if any of the
.gperf files declare conflicting token sets. (gperf itself would have done
this for the simple case of duplicate tokens in the same input file.)

Unbreak for the case where ``make obj'' was run first.

Hello, getconf. This is a slight reinvention of the
wheel^H^H^H^H^HPOSIX.2 and X/Open utility, and rather
more complicated than necessary.