Add support for serial and null console to UEFI boot loader.
Set PKG_CACHEDIR to an 'All/' directory one level lower
to fix 'pkg repo' generating repository metadata for the
on-disc packages.

MFC after:	3 days
X-MFC-to-10.1:	yes
Sponsored by:	The FreeBSD Foundation
Add support for adding empty partition entries. I.e. skip partition
numbers or names. This gives more control over the actual layout and
helps to construct BSD disklabels with /usr or /var at dedicated
partitions.

Obtained from:	Juniper Networks, Inc.
MFC after:	3 days
Relnotes:	yes
Fix duplicate PKG_ABI in the PKG_CACHEDIR path.

MFC after:	3 days
X-MFC-With:	r271480
Sponsored by:	The FreeBSD Foundation
- Don't let rman_reserve_resource() activate the resource in
  nexus_alloc_resource() and don't set a bushandle.
  nexus_activate_resource() will set a proper bushandle.
- Implement a proper nexus_release_resource().
- Fix ixppcib_activate_resource() to call rman_activate_resource()
  before creating a mapping for the resource.

Tested by:	jmg
Fix 'function declaration isn't a prototype' warning.

Pointed by:	ian
MFC after:	1 week
Simplify vntype_to_kinfo() by returning when the desired value is found
instead of breaking out of the loop and then immediately checking the loop
index so that if it was broken out of the proper value can be returned.

While here, use nitems().
Pass the length of an structure to the pretty-printer backends as a
size_t instead of an int.
Tweak pipe_truncate() to more closely match pipe_chown() and pipe_chmod()
by checking PIPE_NAMED and using invfo_truncate() for unnamed pipes.
Fix various issues with invalid file operations:
- Add invfo_rdwr() (for read and write), invfo_ioctl(), invfo_poll(),
  and invfo_kqfilter() for use by file types that do not support the
  respective operations.  Home-grown versions of invfo_poll() were
  universally broken (they returned an errno value, invfo_poll()
  uses poll_no_poll() to return an appropriate event mask).  Home-grown
  ioctl routines also tended to return an incorrect errno (invfo_ioctl
  returns ENOTTY).
- Use the invfo_*() functions instead of local versions for
  unsupported file operations.
- Reorder fileops members to match the order in the structure definition
  to make it easier to spot missing members.
- Add several missing methods to linuxfileops used by the OFED shim
  layer: fo_write(), fo_truncate(), fo_kqfilter(), and fo_stat().  Most
  of these used invfo_*(), but a dummy fo_stat() implementation was
  added.
cxgbe(4): add support for the SIOCGI2C ioctl.