Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r226422, r227241, r228063, r228697, r228698, r228701, r234310, r234850,
r250226, r250926.

This brings m4 up to date with the version in head and fixes the eval
command when called with a 2nd and 3rd argument. The only differences
remaining are related to the updated flex and byacc in head.

PR: bin/166994

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Kill extraneous whitespace.

Functions declared as <type> <identifier>(<nil>) should be declared as
<type> <identifier>(<void-type>) in ANSI C.

Revert vendor identifiers, and #if 0 what is #if 0/#else for OpenBSD.

Add __FBSDID() properly.

Requested by: bde, mike

Merge local changes again, against ANSIfied m4(1).

Crank WARNS.

Cast sizeof() to (int), as it's being compared against an int, not a size_t.
If i is changed to a size_t, it means the logic must be slightly changed later
in the flow, where --i is checked to be >= 0. I am not sure I want to make a
logic change to account for clearing up a warning, when an aesthetic one will
keep from modifying the logic.

Other harmless casts, that I think I've made in the right directions.

Make gpbc() an inline function, rather than an obfuscated macro, make its
scratch space local, rather than global. The previous macro used a dirty
hack (logical AND in place of a conditional) which would lead GCC to throw
a fit (rightly so) as the logical check, as well as the incrementation of
a variable, were not used for anything.

const'ify a few places where gcc3 yells. xstrdup() some global consts in
places where we xstrdup() when not using consts, but tried to assign them
to non-consts before.

Don't use execv(2) if we don't have the kind of arguments it wants.

Reviewed by: asmodai obrien tjr
Submitted by: tjr (a gcc3 build log)

Bring OpenBSD m4(1) off of the OPENBSD vendor branch, and add the -s option,
$FreeBSD$ identifiers, and fix initialisation to stderr to happen in a function
as stderr is not the same in CURRENT as in OpenBSD.

Reviewed by: obrien

This commit was generated by cvs2svn to compensate for changes in r90744,
which included commits to RCS files with non-trunk default branches.

Import OpenBSD m4 as of today.