Implement FIODTYPE for master ptys.

Requested and reviewed by:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Change the deadfs poll VOP to return POLLIN|POLLRDNORM if the caller
is interested in i/o state.  Return POLLNVAL for invalid bits, similar
to poll_no_poll().  Note that POLLOUT must not be returned, since
POLLHUP is set.

Noted and reviewed by:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
When vnode bypass cannot be performed on the cdev file descriptor for
read/write/poll/ioctl, call standard vnode filedescriptor fop.  This
restores the special handling for terminals by calling the deadfs VOP,
instead of always returning ENXIO for destroyed devices or revoked
terminals.

Since destroyed (and not revoked) device would use devfs_specops VOP
vector, make dead_read/write/poll non-static and fill VOP table with
pointers to the functions, to instead of VOP_PANIC.

Noted and reviewed by:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Style changes for deadfs:
- ANSIfy VOPs.
- Remove trivial comments.
- Remove ARGSUSED.
- Remove copies of the vop_XXX_args structure definitions in comments.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Update the OFED Linux compatibility layer and
Mellanox hardware driver(s):

- Properly name an inclusion guard
- Fix compile warnings regarding unsigned enums
- Add two new sysctl nodes
- Remove all empty linux header files
- Make an error printout more verbose
- Use "mod_delayed_work()" instead of
  cancelling and starting a timeout.
- Implement more Linux scatterlist
  functions.

MFC after:	3 days
Sponsored by:	Mellanox Technologies