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)

Set magic fbsd:nokeywords property that allows files to bypass
keyword expansion. (file-specific replacement for CVSROOT/exclude)

Repo-copy tools/regression/usr.bin/make to tools/build/make_check
and adjust the path in the Makefile for the upgrade_checks target.
These checks are really feature upgrade checks that should be fast
and just find out whether we need to build a new make before
proceeding with other targets like buildworld. This makes the
place free for a real regression test suite in the old place.

Add some regression tests for the .SHELL target. I'm not sure that the
output of shell_2j is actually correct - it just tests what make currently
does. Make should switch on echoing for the second line, shouldn't it?