MFC r276737,r289369,r289376,r289424,r291219,r291382,r291385,r291908:

r276737 (by imp):

Remove old ioctl use and support, once and for all.

r289369 (by emaste):

newfs_msdos: rework option parsing to match NetBSD

NetBSD split newfs_msdos in two so that they can reuse the file system
creation part in makefs. This change is a step on the path of bringing
that support to FreeBSD.

Reviewed by: kib, pfg
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D3905

r289376 (by emaste):

newfs_msdos: move mkfs_msdos to separate file for later use in makefs

Sponsored by: The FreeBSD Foundation

r289424 (by emaste):

newfs_msdos: prefer snprintf to sprintf

Obtained from: NetBSD
Sponsored by: The FreeBSD Foundation

r291219 (by emaste):

newfs_msdos: rework error handling for eventual use in makefs

Return -1 on errors from mkfs_msdos() instead of err()/errx(), to
allow different consumers to handle errors as appropriate.

Obtained from: NetBSD
Sponsored by: The FreeBSD Foundation

r291382 (by emaste):

mkfs_msdos: sync with NetBSD

Add a sanity test and clean up whitespace.

Obtained from: NetBSD

r291385 (by emaste):

Use netbsd usage() implementation in newfs_msdos

In r289629 newfs_msdos option descriptions are available in
mkfs_msdos.h.

Obtained from: NetBSD

r291908:

Fix leak in mkfs_msdos(..) by initializing img to NULL and free'ing at the end
of the function

Differential Revision: https://reviews.freebsd.org/D4405
PR: 204943
Reviewed by: emaste, jilles
Reported by: David Binderman <dcb314@hotmail.com>
Sponsored by: EMC / Isilon Storage Division