'RELENG_6_0_0_RELEASE'.

This commit was manufactured to restore the state of the 6.0-RELEASE image.

HEAD to RELENG_6: changes to introduce a credentialed version of the
clone event handler, and then changes to merge the regular and
credentialed versions into a single interface (along with updates to
existing consumers).  With this merge, 6.x and 7.x are in sync.

First batch merges devfs_devs.c:1.37, devfs_vnops.c:1.115,
kern_conf.c:1.187, tty_pty.c:1.138, mac_vfs.c:1.109, mac_biba.c:1.36,
mac_lomac.c:1.36, mac_mls.c:1.73, mac_stub.c:1.53, mac_test.c:1.61,
conf.h:1.223, mac.h:1.68, mac_policy.h:1.67 from HEAD to RELENG_6:

  When devfs cloning takes place, provide access to the credential of the
  process that caused the clone event to take place for the device driver
  creating the device.  This allows cloned device drivers to adapt the
  device node based on security aspects of the process, such as the uid,
  gid, and MAC label.

  - Add a cred reference to struct cdev, so that when a device node is
    instantiated as a vnode, the cloning credential can be exposed to
    MAC.

  - Add make_dev_cred(), a version of make_dev() that additionally
    accepts the credential to stick in the struct cdev.  Implement it and
    make_dev() in terms of a back-end make_dev_credv().

  - Add a new event handler, dev_clone_cred, which can be registered to
    receive the credential instead of dev_clone, if desired.

  - Modify the MAC entry point mac_create_devfs_device() to accept an
    optional credential pointer (may be NULL), so that MAC policies can
    inspect and act on the label or other elements of the credential
    when initializing the skeleton device protections.

  - Modify tty_pty.c to register clone_dev_cred and invoke make_dev_cred(),
    so that the pty clone credential is exposed to the MAC Framework.

  While currently primarily focussed on MAC policies, this change is also
  a prerequisite for changes to allow ptys to be instantiated with the UID
  of the process looking up the pty.  This requires further changes to the
  pty driver -- in particular, to immediately recycle pty nodes on last
  close so that the credential-related state can be recreated on next
  lookup.

  Submitted by:   Andrew Reisse <andrew.reisse@sparta.com>
  Obtained from:  TrustedBSD Project
  Sponsored by:   SPAWAR, SPARTA

Second batch merges scsi_target.c:1.68, coda_fbsd.c:1.43,
firewirereg.h:1.38, fwdev.c:1.47, nmdm.c:1.36, snp.c:1.100, dsp.c:1.82,
mixer.c:1.45, vkbd.c:1.9, devfs_vnops.c:1.117, tty_pty.c:1.139,
tty_tty.c:1.57, bpf.c:1.156, if_tap.c:1.56, if_tun.c:1.153,
smb_dev.c:1.28, conf.h:1.224 from HEAD to RELENG_6:

  Merge the dev_clone and dev_clone_cred event handlers into a single
  event handler, dev_clone, which accepts a credential argument.
  Implementors of the event can ignore it if they're not interested,
  and most do.  This avoids having multiple event handler types and
  fall-back/precedence logic in devfs.

  This changes the kernel API for /dev cloning, and may affect third
  party packages containg cloning kernel modules.

  Requested by:   phk

These changes modifies the kernel device driver API for device cloning,
and might require minor modifications to third party device drivers that
make use of devfs cloning.  It will not be merged to RELENG_5.

Approved by:	re (scottl)

closes the race where the cdev was reclaimed before it ever made it
back to devfs lookup.

null-modem tty device emulate the speed settings faithfully.

The speed is emulated independently for the two directions, using
the slower of the local sides ispeed and the remote sides ospeed.

The emulated speed takes settings of bits/char, parity and stopbit
into account.

Inspired by:	The BSD-DK Editor Celebrity Deathmatch Contest

modes on a tty structure.

Both the ".init" and the current settings are initialized allowing
the function to be used both at attach and open time.

The function takes an argument to decide if echoing should be enabled.
Echoing should not be enabled for regular physical serial ports
unless they are consoles, in which case they should be configured
by ttyconsolemode() instead.

Use the new function throughout.

future:

rename ttyopen() -> tty_open() and ttyclose() -> tty_close().

We need the ttyopen() and ttyclose() for the new generic cdevsw
functions for tty devices in order to have consistent naming.

Tested by:	ambrisko

The big lines are:
	NODEV -> NULL
	NOUDEV -> NODEV
	udev_t -> dev_t
	udev2dev() -> findcdev()

Various minor adjustments including handling of userland access to kernel
space struct cdev etc.