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

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

Rename GEOM class kernel module g_md.ko to geom_md.ko for consistency
with the rest.

mdconfig.c: Simplify mdmaybeload() function.
mdioctl.h: Removed (now unused) #define.
loader.conf: Sort GEOM classes properly.

OK'ed by: phk

change the name of the md module, to g_md, introduce a define with the
name MD_MODNAME, and make mdconfig use this new define...

Add opt_geom.h to the list.

Drop <bsd.man.mk> support from <bsd.kmod.mk>.

Not objected to by: -current

Remove vestiges of MFS.

Use a consistent style and one much closer to the rest of /usr/src

Add a missing vnode_if.h.

Submitted by: Jim Bloom <bloom@acm.org>

Avoid the modules madness I inadvertently introduced by making the
cloning infrastructure standard in kern_conf. Modules are now
the same with or without devfs support.

If you need to detect if devfs is present, in modules or elsewhere,
check the integer variable "devfs_present".

This happily removes an ugly hack from kern/vfs_conf.c.

This forces a rename of the eventhandler and the standard clone
helper function.

Include <sys/eventhandler.h> in <sys/conf.h>: it's a helper #include
like <sys/queue.h>

Remove all #includes of opt_devfs.h they no longer matter.

Add dummy opt_devfs.h file.

Use .include <bsd.kmod.mk> to get to ../../*/conf/kmod.mk instead of
encoding the relative path.

Pull in sys/conf/kmod.mk, rather than /usr/share/mk/bsd.kmod.mk.
This means that the kernel can be totally self contained now and is not
dependent on the last buildworld to update /usr/share/mk. This might
also make it easier to build 5.x kernels on 4.0 boxes etc, assuming
gensetdefs and config(8) are updated.

Removed special rules for building and cleaning device interface files
and empty options files. The rules are now generated automatically in
bsd.kmod.mk. Cleaned up related things ($S and ${CLEANFILES}).

This fell out of a previous commit: create the opt_md.h and opt_mfs.h
files for the md module.

Add phk's m(4) Memory Disk driver as a KLD. I don't believe it
works properly after unloading, however.