- MFi386: Add compile-with option for tau32-ddk.c.
- Whitespace change.
- Remove duplicate line.
Reduce diffs against i386.
Merge pc98's machdep.c into i386/i386/machdep.c.
MFV r272493:

Show individual disk capacity when doing zpool list -v.

Illumos issue:
    5147 zpool list -v should show individual disk capacity

MFC after:	1 week
Add sequence counters with memory barriers.

Current implementation is somewhat simplistic and hackish,
will be improved later after possible memory barrier overhaul.

Reviewed by:	kib
MFC after:	3 weeks
MFV r272494:

Make space_map_truncate() always do space_map_reallocate().  Without
this, setting space_map_max_blksz would cause panic for existing pool,
as dmu_objset_set_blocksize would fail if the object have multiple blocks.

Illumos issues:
   5164 space_map_max_blksz causes panic, does not work
   5165 zdb fails assertion when run on pool with recently-enabled
	spacemap_histogram feature

MFC after:	2 weeks
Plug capability races.

fp and appropriate capability lookups were not atomic, which could result in
improper capabilities being checked.

This could result either in protection bypass or in a spurious ENOTCAPABLE.

Make fp + capability check atomic with the help of sequence counters.

Reviewed by:	kib
MFC after:	3 weeks
MFV r272495:

In arc_kmem_reap_now(), reap range_seg_cache too to reclaim memory in
response of memory pressure.

Illumos issue:
    5163 arc should reap range_seg_cache

MFC after:	1 week
MFV r272496:

Add tunable for number of metaslabs per vdev
(vfs.zfs.vdev.metaslabs_per_vdev).  The default remains
at 200.

Illumos issue:
    5161 add tunable for number of metaslabs per vdev

MFC after:	2 weeks
Add in decode for the AR9300 RX descriptor.
Diff reduction with upstream.  The code change is not really applicable
to FreeBSD.

Illumos issue:
    5148 zvol's DKIOCFREE holds zfsdev_state_lock too long

MFC after:	1 month
Add a new sysctl, vfs.zfs.vol.unmap_enabled, which allows the system
administrator to toggle whether ZFS should ignore UNMAP requests.

Illumos issue:
    5149 zvols need a way to ignore DKIOCFREE

MFC after:	2 weeks
MFV r272499:

Illumos issue:
    5174 add sdt probe for blocked read in dbuf_read()

MFC after:	2 weeks
Make autofs use shared vnode locks.

Reviewed by:	kib
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation