DEVFS and serial numbers

[Matthew Dillon]

    Initial serial number support is now on master.  Serial numbers show
    up in the /dev/serno directory.  All CAM and NATA drives which attach
    with serial numbers will show up.  Note that many USB drives do not
    report serial numbers and may not show up in any meaningful way.

    The original drive names, i.e. da/cd/ad* also still show up in /dev,
    of course.

    Over the course of this week I will be tying the serial number support
    into a new /etc/devtab mechanism that will allow physical drives to
    be named and mounted by name from the fstab.

    Ultimately this will tie into a larger iSCSI mechanic which will
    allow drive mobility.  We probably won't have iSCSI root-mount support
    working for the release, but you never know :-).  Antonio's iSCSI work
    is slated for integration in the next two weeks.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>