ZFS boot support for bhyveload.

Modelled after the i386 zfsloader. However, with no
2nd stage zfsboot to search for a bootable dataset,
attempt a ZFS boot if there is more than one ZFS
dataset found during the disk probe.

sys/boot/userboot/zfs
 - build the ZFS boot library

sys/boot/userboot/userboot/
 conf.c
  - Add the ZFS pool and filesystem tables
 devicename.c
  - correctly format ZFS devices
 main.c
  - increase the size of the libstand malloc pool
  to account for the increased usage from ZFS buffers
  - probe for a ZFS dataset, and if one is
  found, attempt to boot from it.

usr.sbin/bhyveload/bhyveload.c
 - allow multiple invocations of the '-d' option
 to specify multiple disks e.g. a raidz set.
 Up to 32 disks are supported.

Tested with various combinations of GPT, MBR, single
and multiple disks, RAID-Z, mirrors.

Reviewed by:	neel
Discussed with:	avg
Tested by:	Michael Dexter and others
MFC after:	3 weeks
Grammar fix

Submitted by:	Warren Block wblock AT wonkity.com
Simplify the way the end of a singly linked list is followed (for adding
items), so it is more obvious that we aren't going to indirect through
a NULL pointer.

PR:		144723
Submitted by:	Garrett Cooper <yaneurabeya at gmail.com>
Obtained from:	NetBSD r1.19
MFC after:	2 weeks
Increase alignment to size of pointer if the alignment is too small.
Some modules do not align data at least to size of pointer, they uses a
smaller alignment, but our pointer should be aligned to its native
boundary, otherwise on some platforms, hardware alignment checking
will cause bus error.
Rename WITHOUT_DMA into WITHOUT_DMAGENT to avoid confusion

Requested by:	ian
Regen after WITHOUT_DMA -> WITHOUT_DMAGENT renaming
Allow the ubldr boot device to be choosen by a u-boot environment variable.

If a "loaderdev=<device>" env variable is set and the named device
exists, it is used.  If the device doesn't exist, fall back to the
historic "probe" loop that prefers disk devices over network devices.

If the env var is not set, preserve the historic behavior of using the
first working disk device provided by u-boot, or a network device if no
functional disk device is found and a network device exists.

The old probe loop is reworked so that it checks all bootable devices
provided by u-boot rather than taking an early-out on the first device
found.  This results in the cosmetic change of listing all potential boot
devices for the user, but the behavior of which device it chooses is the
same as it has always been.
When the kernel is running in a virtual machine, it cannot rely upon the
processor family to determine if the workaround for AMD Family 10h Erratum
383 should be enabled.  To enable virtual machine migration among a
heterogeneous collection of physical machines, the hypervisor may have
been configured to report an older processor family with a reduced feature
set.  Effectively, the reported processor family and its features are like
a "least common denominator" for the collection of machines.

Therefore, when the kernel is running in a virtual machine, instead of
relying upon the processor family, we now test for features that prove
that the underlying processor is not affected by the erratum.  (The
features that we test for are unlikely to ever be emulated in software
on an affected physical processor.)

PR:		186061
Tested by:	Simon Matter
Discussed with:	jhb, neel
MFC after:	2 weeks
Change fdt_setup_fdtp() from "guess then fail" to more probe-like behavior.

The old code basically said it was going to use some particular blob
without knowing whether it could successfully do so, then it would invoke
the function to do that and return its status.  If it failed, you were
done, even if other blobs might be available.  Now the code attempts to use
some particular blob and if that succeeds it says so and returns success,
otherwise it moves on to try another potential blob.

One specific problem this solves is when u-boot sets an fdtaddr variable
to point to some memory address, then doesn't actually load a blob at
that address.  Now the header check will fail, and the code will move
on to the fallback dtb compiled into the kernel (if any).
Improve logging of send errors, reporting error code and interface.
Reduce code duplication between INET and INET6.

Tested by:	Lytochkin Boris <lytboris gmail.com>
bsd-family-tree: Add DragonFly 3.6.1 to the tree.
bsd-family-tree: Add DragonFly 3.6.1 to the tree.
Change file_loadraw() from static to public.  Change the order of its
arguments from type,filename to filename,type to be consistant with other
public file_whatever() functions, and change it to return a pointer to
the preloaded_file struct describing the file.  Adjust existing callers.
ext2fs: fully enable ext4 read-only support.

The ext4 developers tend to tag Ext4-specific flags as
"incompatible" even when such features are not relevant for
read-only support.  This is a consequence of the process
though which this filesystem is implemented without design
and the fact that some new features are not extensible to
ext2/3.

Organize the features according to what we support and sort
them so that we can now read-only mount filesystems with
some features that may be found in newly formatted ext4 fs.

Submitted by:	Zheng Liu
Reviewed by:	pfg
MFC after:	5 days
Add a feature for automatically finding and loading a dtb file by name.
The name is taken from the u-boot env vars fdtfile or fdt_file.  If the
name isn't fully-qualified a search is done in module_path locations.

The search order for a usable dtb in fdt_setup_fdtp() is now

 - A dtb loaded with an explicit "load -t dtb" command.
 - A dtb already loaded into memory somehow[*] and pointed to by fdt_to_load.
 - A dtb in the memory pointed to by the u-boot env vars fdtaddr or fdt_addr.
 - A file named by the u-boot env vars fdtfile or fdt_file.
 - A static dtb compiled into the kernel.

* Presumably by some arch-specific command or code.
Remove KASSERT from in6p_lookup_mcast_ifp().

When the devel/jenkins port, version 1.551 was started,
the kernel would panic if INVARIANTS was enabled in the kernel config.

Suggested by: bms
Add the FREEBSD_BOOT_LOADER option so that a loaded DTB passed in from
ubldr will actually get used.
Create a generic IMX6 kernel config.  This is based on the existing
WANDBOARD.common config, but with the freescale-specific optons and devices
all together at the bottom now.  In addition to reformatting and shuffling
lines around, two new options are added because they're now known to work,
VFP and FREEBSD_BOOT_LOADER.

This config does not include any static DTB, it requires that u-boot
provide a DTB (or a custom kernel config can compile one in).

This will supercede all the existing WANDBOARD* configs, but those will
be left around for a while to help people transition their customized
configs to include this new one instead.
Don't force bootverbose on anymore, it can be set from ubldr now.
[automated] Merge in upstream-github/master