Permit changing MTU in 6to4 relay.

This behavior is recommended by RFC 4213 clause 3.2.

Sometimes fragmentation is the least evil.
For example, some Linux IPVS kernels forwards
ICMPv6 checksums to real servers incorrectly.
MFC r248672:

Compile contrib/tzcode/stdtime/localtime.c with -fwrapv, since it relies
on signed integer overflow wrapping.  Otherwise mktime(3) and timegm(3)
can hang, in case the timestamp passed in struct tm is not representable
in a time_t.  Specifically, any timestamp after 2038-01-19 03:14:07, in
combination with a 32-bit time_t.

Note that it would be better to change the code to not rely on undefined
behaviour, but it is contributed code, and it is not entirely trivial to
fix the issue properly.
MFC r245266:
Remove not very useful printf, that can be too chatty.

ASUS P8Z77-V board reports _AC2, _AC3 and _AC4 setpoints as 0C.  With active
cooling already automatically set to _AC2, that still caused driver to print
two useless lines about temperature above _AC3 and _AC4 every ten seconds.
Three setponts of 0C is probably a board bug, but the same spam could happen
also in correct case if system is runnign not with the lowest cooling level.
MFC r248788 (erwin):

Update BIND to 9.8.4-P2

Removed the check for regex.h in configure in order
to disable regex syntax checking, as it exposes
BIND to a critical flaw in libregex on some
platforms. [RT #32688]
MFC r248276:
Rewrite the vfs_bio_clrbuf(9) to not access the b_data for B_VMIO
buffers directly, use pmap_zero_page_area(9) for each zeroing page
region instead.
MFC r248277:
Remove excessive and inconsistent initializers for the various kernel
maps and submaps.
MFC r248280:
Add pmap function pmap_copy_pages().
MFC 247266

Don't try and negotiate sync mode if either period or offset are zero.
MFC r244183 by glebius:

  Fix problem in r238990 (MFC'd in r240313).  The LLE_LINKED flag should be
  tested prior to entering llentry_free(), and in case if we lose the race,
  we should simply perform LLE_FREE_LOCKED().  Otherwise, if the race is
  lost by the thread performing arptimer(), it will remove two references
  from the lle instead of one.

  Reported by:	Ian FREISLICH <ianf clue.co.za>
MFC r248226:
  r241438 broke IPMI access on Sun Fire X2200 M2(BCM5715).
  Fix the IPMI regression by sending BGE_FW_DRV_STATE_UNLOAD to
  ASF/IPMI firmware in driver attach phase.  Sending heartheat to
  ASF/IPMI is enabled only after upping interface so
  setting driver state to BGE_FW_DRV_STATE_START in attach phase
  broke IPMI access.
  While I'm here, add NVRAM arbitration lock before performing
  controller reset. ASF/IPMI firmware may be able to access the NVRAM
  while controller reset is in progress.  Without the arbitration
  lock before resetting the controller, ASF/IPMI may not initialize
  properly.
MFC r248319:
Merge vn_io_fault_pgmove().
MFC r248325:
Add my copyright for the 2012 year work, in particular vn_io_fault()
and f_offset locking.  Add required Foundation notice for r248319.

MFC r248329:
Separate the copyright lines and the informational block by a blank line.
MFC r248857:
 - Update hardware notes to reflect that amd64 is no longer "young"
 - Bump copyright year
Merge 248070.

Fix long-standing issue with interface routes being unprotected:
Use RTM_PINNED flag to mark route as immutable.
Forbid deleting immutable routes without special rtrequest1_fib() flag.
Adding interface address with prefix already in route table is handled
by atomically deleting old prefix and adding interface one.
Remove (harmless) duplicate entry for VersionAddendum.

Noticed by:	dim@
MFC after:	1 week
MFC r248854:

  Reverse the order of some implicit commands (FS mounts and ifconfigs)
  when stopping jails.  This matters particularly for nested filesystem
  mounts.

PR:		kern/177325
Submitted by:	Harald Schmalzbauer
MFC r246293: zfs: fix, improve and re-organize page_lookup and page_unlock
MFC r248640: fbt_typoff_init: fix an off by one in determining required
memory size
MFC r248642: fbt_getargdesc: correctly handle types for return probes
MFC r248697:
  When we are removing a specific set, call ipfw_expire_dyn_rules only once.