Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

o confstr(3) returns 0 on error. Check the return value accordingly.

PR: misc/106414
MFC after: 1 week

Warns fixes. Mainly unused headers/params/vars removal, but also
some malloc cleanup.

Tidy up usage message.

Replace an alloca() call with a slightly more standard malloc()/free()
pair.

Add new 1003.1-2001/TC1/D6 parameters. (On final recirculation ballot now,
so this should be officially TC1 before the New Year.)

Add TrustedBSD pathconf parameters.

Add compilation support for -stable (to be merged momentarily).

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.)

Consistently use FBSDID

confstr() returns (size_t)-1 on failure. Check for this explicitly instead
of trying to see if an unsigned number is less than zero.

Destroy the evidence of my misunderstanding of the specification.
Also fix up the phrasing in the man page a bit.

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.