Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Sync program's usage() with manpage's SYNOPSIS.

o __P removal
o register removal
o use new style prototypes and function definitions

Don't call err() without a format string.

$Id$ -> $FreeBSD$

Use warn(3). Hardcode progname instead of using argv[0]. Use Pa for file
name.

Many places in the code NULL is used in integer context, where
plain 0 should be used. This happens to work because we #define
NULL to 0, but is stylistically wrong and can cause problems
for people trying to port bits of code to other environments.

PR: 2752
Submitted by: Arne Henrik Juul <arnej@imf.unit.no>

compare return value from getopt against -1 rather than EOF, per the final
posix standard on the topic.

Revert $FreeBSD$ to $Id$

Make the long-awaited change from $Id$ to $FreeBSD$

This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.

Close PR #2193: support backslash line continuations.
(Also did some minor cleanups.)

Use err() instead of perror()/exit() and remember to #include <errno.h>
and <err.h>.

Small touchups:

- Fix typos in comments in hash.c.
- Remove unneeded and unused member from grouplist struct in hash.h.
(Curiously, the compiler never complained about this even though the
member was of type 'struct grps' which is not defined anywhere in
this program.)
- char ch -> int ch in revnetgroup.c.
- char *argv[0]; -> char *argv[]; also in revnetgroup.c.
- Force the user to specify at least one of the -u or -h flags
and complain if they specify both.

This commit was generated by cvs2svn to compensate for changes in r11814,
which included commits to RCS files with non-trunk default branches.

Import the first cut of my (finally finished) revnetgroup program. This
program parses the /etc/netgroup file into netgroup.byuser and netgroup.byhost
format for NIS.

I used hash tables to store the initial netgroup data in memory and to
construct the 'reverse' netgroup output. It seems just as fast as the
SunOS revnetgroup, which is surprising considering this is my first
attempt at using hash tables in a real application. :)

Note that I canibalized a large chunk of getnetgrent.c to save myself
from having to write my own netgroup parsing functions.