MFC r330245:

Allow the "@" and "!" characters in passwd file GECOS fields.

Two PRs (152084 & 210187) request allowing the "@" and/or "!"
characters in the passwd file GECOS field. The man page for pw does
not mention that those characters are disallowed, Linux supports those
characters in this field, and the "@" character in particular would be
useful for storing email addresses in that field.

PR: 152084, 210187
Submitted by: jschauma@netmeister.org, Dave Cottlehuber <dch@freebsd.org>
Reported by: jschauma@netmeister.org, Dave Cottlehuber <dch@freebsd.org>
Sponsored by: Dell EMC

MFC r322581: remove debug files in delete-old* when WITHOUT_DEBUG_FILES

Sponsored by: The FreeBSD Foundation

MFC: r315912 (by eugen@) and r315935

Properly initialise with content of pw.conf(5) that was mistakenly ignored.
Also, respect "defaultgroup" if specified there.

Add a regression test

PR: 217934
Reported by: Victor Sudakov <vas@mpeks.tomsk.su>

MFC r315776:

Rename tests from <foo> to <foo>_test to match the FreeBSD test suite
naming scheme

usr.bin/diff/diff_test was renamed to usr.bin/diff/netbsd_diff_test
to avoid collisions with the renamed FreeBSD test.