Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with:		pfg
MFC After:		3 days
Sponsored by:		Netflix

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using mis-identified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

thing it was still used for was to set the "global default" password
hash.  Since the stock auth.conf contained nothing but comments, the
global default was actually the first algorithm in crypt(3)'s list,
which happens to be DES; I take the fact that nobody noticed as proof
that it was not used outside of crypt(3).

The only other use in our tree was in the Kerberos support code in
in tinyware's passwd(1).  I removed that code in an earlier commit;
it would not have compiled anyway, as it only supported Kerberos IV.

The auth_getval() function is now a stub that always returns NULL,
which has the same effect as a functional auth_getval() with an
empty auth.conf.

MFC after:	3 weeks

o make property_read() take a fd instead to avoid stdio.h mess
o update auth to new interface.

I'll convert sysinstall to use shortly) and a simple call which uses
this mechanism to implement an /etc/auth.conf file.  I'll let Mark Murray
handle the format and checkin of the sample auth.conf file.
Reviewed by:	markm