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

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

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

Approved by: re (implicit)

Replace "/etc/make.conf" with references to make.conf(5)
where applicable. The main reason for this change is that
the location of make.conf is not constant and can be
modified via __MAKE_CONF. This change also improves
hyper-text linkage in our manpages.

MFC after: 2 weeks

Fix a grammar nit of mine.

-mandoc style tweak rev 1.13.
Submitted by: ru

Catch up with the latest policies on knobs.

[NO]MAN -> NO_[MAN].
Bump doc date.

Fix a spelling error.

mdoc(7): EXAMPLES is the standard section name.

Fixed mispelling of SCRIPTS as SCRIPT.

Document SHLIB, kind of.

mdoc(7): Use the new feature of the .In macro.

Punctuation.

Another traffice ticket for crossing the .'ed line from the mdoc police.

Submitted by: ru

Also allow and document a "build" ordering for variables.
Both "product" and "build" ordering are rampant in /usr/src. This document
is not indented to be as strict as style(9) as historically BSD hasn't been
as consistent about Makefile as C code. Also there are too many variations,
exceptions and allowances in out existing Makefile style to be strict.
However there is a general level of consensus on what the general BSD style
of our Makefiles is. This manpage documents that "smell".

o Do not use VPATH.
o Give the proper spelling for WARNS.
o Clarify using NO_WERROR.
o Embelish -D after -I verbage.
o Document preference of ${.ALLSRC} & ${.TARGET} vs. $< & $@.

Based on: brucification

Mdoc police.

Submitted by: ru

FreeBSD Makefile style guide.

Approved by: TRB