Grammar.

Sponsored by:	EMC / Isilon storage division
The radix preallocation pages can overfow the biggestone segment, so
use a different scheme for preallocation: reserve few KB of nodes to be
used to cater page allocations before the memory can be efficiently
pre-allocated by UMA.

This at all effects remove boot_pages further carving and along with
this modifies to the boot_pages allocation system and necessity to
initialize the UMA zone before pmap_init().

Reported by:	pho, jhb
Fix style.
Remove an unuseful check on resident_page_count.
vm_radix_lookup_ge() of an empty trie is as fast as checking a
NULL pointer.
MFC
Merge from vmcontention.
- Fix style in vm_page_lookup(): there is no whiteline between
  assertions and other code in this file.
- Reinsert some comments that were lost during the work but which are
  actual yet, reducing differences with HEAD.

Sponsoed by:	EMC / Isilon storage division
Improve dynamic branch prediction and i-cache utilization:
- Use predict_false() to tag boot-time cache decisions
- Compact boot-time cache allocation into a separate, non-inline,
  function that won't be called most of the times.

Sponsored by:	EMC / Isilon storage division
- When panicing for "too small boot cache" reason, print the actual
  cache size value
- Add a way to specify the size of the boot cache at compile time

Sponsored by:	EMC / Isilon storage division
Move the radix node zone destructor definition closer to
vm_radix_init() definition.

Sponsored by:	EMC / Isilon storage division
Fix comment.
Remove unused headers.
On arches with VM_PHYSSEG_DENSE  the vm_page_array is larger than
the actual number of vm_page_t that will be derived, so v_page_count
should be used appropriately.

Besides that, add a panic condition in case UMA fails to properly
restrict the area in a way to keep all the desired objects.

Sponsored by:	EMC / Isilon storage division
Reported by:	alc
MFC
Merge from vmcontention
Remove whitespace.
Remove an unuseful check as looking up into an empty trie should be
as fast as checking a NULL ptr.

Sponsored by:	EMC / Isilon storage division
Update vendor/illumos/dist and vendor-sys/illumos/dist
to illumos-gate 13957:512faafc0eaf

Illumos ZFS issues:
  3537 want pool io kstats
Update vendor/illumos/dist and vendor-sys/illumos/dist
to illumos-gate 13957:512faafc0eaf

Illumos ZFS issues:
  3537 want pool io kstats
Switch vm_object lock to be a rwlock.
* VM_OBJECT_LOCK and VM_OBJECT_UNLOCK are mapped to write operations
* VM_OBJECT_SLEEP() is introduced as a general purpose primitve to
  get a sleep operation using a VM_OBJECT_LOCK() as protection
* The approach must bear with vm_pager.h namespace pollution so many
  files require including directly rwlock.h