Fix issue with nmdm and leading zeros in device name.

The nmdm code enforces a number between the 'nmdm' and 'A|B' portions
of the device name. This is then used as a unit number, and sprintf'd
back into the tty name. If leading zeros were used in the name,
the created device name is different than the string used for the
clone-open (e.g. /dev/nmdm0001A will result in /dev/nmdm1A).

Since unit numbers are no longer required with the updated tty
code, there seems to be no reason to force the string to be a
number. The fix is to allow an arbitrary string between
'nmdm' and 'A|B', within the constraints of devfs names. This allows
all existing user of numeric strings to continue to work, and also
allows more meaningful names to be used, such as bhyve VM names.

Tested on amd64, i386 and ppc64.

Reported by:	Dave Smith
PR:		192281
Reviewed by:	neel, glebius
Phabric:	D729
MFC after:	3 days
Fix a boundary case error in vm_reserv_alloc_contig(): If a reservation
isn't being allocated for the last of the requested pages, because a
reservation won't fit in the gap between allocated pages, then the
reservation structure shouldn't be initialized.

While I'm here, improve the nearby comments.

Reported by:	jeff, pho
MFC after:	1 week
Sponsored by:	EMC / Isilon Storage Division
Fix minor buffer overflow reported by Coverity.

CID:		1006781
Fix memory leak on error, reported by Coverity.

CID:		1007773
Fix couple off-by-one range check errors, reported by Coverity.

CID:		1007837
Fix array overrun, reported by Coverity.

CID:		1229970
Remove uninitialized and unused variable, reported by Coverity.

CID:		1230015
Make ctl_port_mask an array to support more then 32 ports.

Overflow reported by Coverity.

CID:		1229894
MFC after:	3 days
Remove many false positives with make checkdpadd

- Reduce DPADD and LDADD in checkdpadd to -l<foo>
- Skip over -Wl,[es]*-group because -Wl,--end-group and
  -Wl,--start-group might be required to properly link objects (see
  usr.bin/clang/lldb as an example)

This caveat has been present for a while with some components of
the build. However, these false positives were made more more apparent
after r269648.

Phabric: D635
Reviewed by: jmmv (an earlier version)
PR: 192730
MFC after: 2 weeks
Fix memory leak, reported by Coverity.

CID:		1229996
Replace local copy-and-paste implementations of printmbuf() in several
device drivers with calls to the centralised m_print() implementation.
While the formatting and output details differ a little, the content
is essentially the same, and it is unlikely anyone has used this
debugging output in some time.

This change reduces awareness of mbuf cluster allocation (and,
especially, the M_EXT flag) outside of the mbuf allocator, which will
make it easier to refine the external storage mechanism without
disrupting drivers in the future.

Style bugs are preserved.

Reviewed by:	bz, glebius
MFC after:	3 days
Sponsored by:	EMC / Isilon Storage Division