kernel - Add negative caching to cache_findmount()

* Add negative caching to cache_findmount().  It turns out that there
  are quite a few cases, particularly during poudriere, so this is
  needed to avoid dropping down into the slow mountlist scan code.

* Removes remaining bottlenecks in mount-point crossings during path
  lookups.  The mountlist_token is no longer colliding in critical
  paths.
kernel - Remove getnewvnode() bottlenecks

* Move the global mntvnodescan_list into the mount structure and remove
  the global mntvnode_token.  Adjust the code to use the per-mount
  mp->mnt_token instead.

* This removes a major token bottleneck in getnewvnode(), particularly
  important when doing concurrent not-yet-cached directory scans or file
  creates under different mount points, and when the vnode cache reaches
  its nominal maximum.

* Also add a missing piece for the last cache_findmount() commit.
kernel - Fix deadlock in tmpfs

* If the pageout daemon is paging out a file on a tmpfs mount concurrent
  with an unmount of same, a deadlock can occur.

* Fix the node vs vnode lock order in the tmpfs umount code.
kernel - Fix cross-mount handling in tmpfs hardlink code

* Fix tmpfs to properly report EXDEV when a cross-mount hardlink is
  attempted instead of asserting and causing a panic.

Reported-by: ftigeot
iso639: Add Standard Moroccan Tamazight.

See http://www.loc.gov/standards/iso639-2/php/code_changes.php
hier.7: Document that /boot/kernel is a directory and has the modules too.

While here, also remove /usr/include/objc.
libdmsg: Fix pointer dereference.
Use NULL for pointers in a couple of places.
kernel - cpu_pause() needs to be memory-modifying

* __asm __volatile isn't enough, it also needs the "memory"
  attribute to prevent gcc from optimizing out memory loads around
  loops using cpu_pause().
kernel - Implement shared namecache locks

* Currently highly experimental, so I've added a sysctl and default it
  to disabled for now.

  sysctl debug.ncp_shared_lock_disable
	0	Shared namecache locks enabled
	1	Shared namecache locks disabled (default)

* Removes most conflicts when concurrent processes are doing long path
  lookups with substantially similar prefixes.

* Also removes directory conflicts when concurrent processes are accessing
  different file names under the same directory using short paths.

* Shared mode is only used when the ncp is resolved and in a normal
  working state (this includes entries which have resolved to ENOENT).
  Otherwise the code falls back to exclusive mode.

* Shared namecache locks have three major complexities:

  (1) First, some bits of the nlookup() routine had to be rearranged to
      avoid double locking.  This is because the last namecache component
      always has to be locked exclusively, but a path such as a/b/d/.
      references the same ncp entry for both of the last two components.

  (2) Second, any lock on a namecache structure vhold()'s the related vp
      (if not NULL).  Shared locks present a particular issue where a
      second cpu may obtain a second shared lock before the first cpu
      is able to complete vhold()ing the vnode.  The vnode cannot be
      vhold()'d prior to the lock.  To deal with this an interlock was
      implemented (see NC_SHLOCK_VHOLD).

  (3) Finally, because there might be many concurrent shared lock users
      to avoid starving out an exclusive lock user we must stall further
      shared locks while an exclusive request is pending.

* The implementation specifically does not attempt to implement lock
  upgrading.  That's another can of worms that I'd rather not open.
Merge branch 'master' into gsocdrm_merger