Remove $FreeBSD$: one-line .c pattern

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

pw: Remove unnecessary errp checks.

The caller-supplied pointer is unconditionally dereferenced at the
beginning of the function, so there is no point in comparing it with
NULL thereafter.

Reported by: Coverity
MFC after: 1 week
Sponsored by: NetApp, Inc.
Sponsored by: Klara, Inc.

Fix err pointer not initialized to NULL resulting

Reported by: "O. Hartmann" <ohartman@zedat.fu-berlin.de>

Rewrite parsing subcommands arguments of pw(8)

Now each subcommands checks its arguments in a dedicated functions.

This helps improving input validation, code readability/maintainability
While here:
- Add a -y option to pw userdel/usermod so it can maintain NIS servers if
nispasswd is not defined in pw.conf(5)
- Allow pw -r <rootdir> to remove directory with userdel -r
- Fix bug when renaming a user which was not renaming the user name it groups
it is a member of.
- Only parse pw.conf(5) when needed.

Improve strtounum

Fix many style bugs
Better variable naming
Use C99 'restrict' were apropriate
Fix potential errno race

Submitted by: bde

Actually set the proper license

Reported by: trasz

Actually add the new code