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

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

Atapi units are now /dev/ad* and not /dev/wd*

mount_msdos(8) -> mount_msdosfs(8).

MF4S: Syncronise with Luigi's work in -stable.

Commit PicoBSD mega-patch:
. Bring PicoBSD up to date with -CURRENT reality.
. Make PicoBSD smart and not spam /dev/vn0 and /mnt. Now it uses the first
unused vn device and creates a temporary mountpoint in /tmp.
. Miscellaneous build cleanups and optimizations.

Unfortunately the bridge, isp, and router floppies are too big and need
the axe treatment. The install floppy needs updating to -CURRENT. Dial and
net build and (appear to) run OK. I will be adressing these in the
near future (unless someone beats me to it :-) ).

PR: misc/17737
Submitted by: Omachonu Ogali <oogali@intranova.net>

Cleanup of the default floppy tree for PicoBSD builds.

Approved-by: jordan

Major PicoBSD update by luigi with some debugging help from myself.

. Now builds on -STABLE (-CURRENT is broken due to bugs)
. etc directory contents centralized instead of in each
type directory (can exclude & override as desired)
. Removed extraneous language files (lang files for rc really necessary?)
. dialog-based build tool with support for custom floppy builds
. MFS image loads as a mfs_root module instead of compiled into kernel

THIS IS BROKEN ON CURRENT. I'll MFC to -STABLE immediately following.
luigi tells me I have an OK from jkh on the MFC.

Submitted by: luigi