kernel - Cluster fixes + Enable clustering for HAMMER1

* Add cluster_awrite(), which replaces vfs_bio_awrite() and has the same
  basic semantics as bawrite().

* Remove vfs_bio_awrite(), which had an odd API that required the buffer
  to be locked but not removed from its queues.

* Make cluster operations work on disk device buffers as well as on
  regular files.

* Add a blkflags argument to getcacheblk(), allowing GETBLK_NOWAIT to
  be passed to it.

* Enhance cluster_wbuild() to support cluster_awrite() by having it take
  an optional bp to incorporate into the cluster.  The caller disposes of
  the bp by calling bawrite() if the cluster_wbuild() code could not use it.

* Certain adjustments to cluster_write() and related code in checking against
  the file EOF to not break when variable block sizes are used.

* Fix a bug in calls made to buf_checkwrite().  The caller is required to
  initiate the I/O if the function returns good (0).  HAMMER1 uses this
  save side effects and blows up if the I/O is then not initiated.

* Enable clustering in HAMMER1 for both data and meta-data.
kernel - Fix three AHCI bugs

* This fixes spurious timeouts which occur on SMP boxes with faster devices
  (such as SSDs or more recent hard drives)

* The global interrupt status register appears to be latched on some parts
  rather than wire-or.  Clearing it after signaling the port threads or
  processing the interrupt can cause interrupts to be lost.

* In cases where it is actually wire-or we may get a double-interrupt,
  but stability is more important here.

* Fix the port signaling code.  The mask was being cleared with the
  port interlock released.  It has to be cleared when the interlock is
  held.

* Reorder the per-port interrupt status register clearing code in two
  places to execute before processing the operation rather than after,
  which may fix another source of lost interrupts.
kernel - Fix mount refs interactions and umount races

* It is possible for a umount to race other operations on active mount
  point, causing one or the other to deadlock.

* vfs_busy()/vfs_unbusy() now incr/decr mp->mnt_refs.

* cache_findmount() now increments mp->mnt_refs, and add a new API
  function cache_dropmount() which decrements it.
tcp/sack: Add comment about the implemented TCP/SACK related RFCs
kernel - Fix another AHCI bug

* Remove the unlock/lock sequences around the xpt_done() calls.  These
  temporary unlocks create a gap which can allow another interrupt to
  squeeze in and interfere with the interrupt thread that is already
  running, resulting in corruption.

  This bug occurs under very heavy loads, and typically required multiple
  concurrent ops to a SSD to trigger.

* Add additional assertions to catch issues and reorder one of the
  chiploads.

* This is a bit non-optimal, be on the lookout for deadlocks in case it
  turns out that holding the lock is a bad idea.
kernel - Fix bug in SILI, remove debugging in AHCI

* Fix the same unlock/lock sequence bug in the SILI driver that was
  fixed in the AHCI driver.

* Remove a flag that was being added to the service set in AHCI for
  debugging purposes.
kernel - Fix improper unlock/relock sequence in HAMMER

* VOP_FSYNC() can be called during a vnode inactivation or reclaim.
  In this case the vnode lock absolutely cannot be released or it
  can create a window of opportunity for another thread that results
  in a panic.

* Fixes a NFS server crash when multiple clients are trying to
  delete/create/write the same file at the same time.
kernel - Improve NFS server error responses when an inode goes away

* When an inode goes away and FHTOVP fails return ESTALE instead of
  what the VFS returned.

* Greatly improves the re-acquisition of files on NFS clients which have
  been ripped out by the server or other clients.
rpc.yppasswdd(8): Fix some warnings and raise WARNS to 5.
kernel - Add workaround for errata #721 on AMD cpus (found by Matt Dillon)

* Official reference for errata 721:

    http://support.amd.com/us/Processor_TechDocs/41322_10h_Rev_Gd.pdf

* This is the cpu bug found by Matthew Dillon, present on all K10 cores
  (so far).  AMD has indicated that the bug is not present on Bulldozer
  cpus.

* The MSR workaround is now reported and programmed during kernel boot.

* No discernable difference in performance was detected running GCC
  with and without the MSR adjustment.

* Verified to have fixed our test case w/GCC.  It no longer seg-faults.
libc - Do not allow a stuck syslogd to screw up the entire system

* If syslogd gets stuck the socket buffer will still full forever.
  Only try writing a limited number of times before giving up.
vquota(8): Only count files with more than 2 hard links once

True, false, what's the difference ?
VFS accounting: fix an issue with unlink operations

* Space counters were previously decreased for every unlink(2)
  on regular files.

* They are only updated for the last link now
ELF: Update header, sync with binutils 2.22
rtld: Implement DT_RUNPATH and -z nodefaultlib

DT_RUNPATH is incorrectly being considered as an alias of DT_RPATH.  The
purpose of DT_RUNPATH is to have two different types of rpath: one that
can be overridden by the environment variable LD_LIBRARY_PATH and one that
can't.  With the currently implementation, LD_LIBRARY_PATH will always
trump any embedded rpath or runpath tags.

Current path search order by rtld:
==================================
LD_LIBRARY_PATH
DT_RPATH / DT_RUNPATH (always the same)
ldconfig hints file (default: /var/run/ld-elf.so.hints)
/usr/lib

New path search order by rtld:
==============================
DT_RPATH of the calling object if no DT_RUNPATH
DT_RPATH of the main binary if no DT_RUNPATH and binary isn't calling obj
LD_LIBRARY_PATH
DT_RUNPATH
ldconfig hints file
/usr/lib

The new path search matches how the linux runtime loader works.  The other
major added feature is support for linker flag "-z nodefaultlib".  When
this flag is passed to the linker, rtld will skip all references to the
standard library search path ("/usr/lib" in this case but it could handle
more color delimited paths) except in DT_RPATH and DT_RUNPATH.

New path search order by rtld with -z nodefaultlib flag set:
============================================================
DT_RPATH of the calling object if no DT_RUNPATH
DT_RPATH of the main binary if no DT_RUNPATH and binary isn't calling obj
LD_LIBRARY_PATH
DT_RUNPATH
ldconfig hints file (skips all references to /usr/lib)

Currently gcc41 and gcc44 are embedding /usr/lib directly in every
DT_RPATH tag of every binary and shared library it creates.  This is
both unnecessary due to rtld default search path order and it also
defaults the purpose of -z nodefaultlib, so this behavior must be
changed before the flag works.  This will be done in a separate commit.
gcc44: remove /usr/lib from rpath

The gcc44 specs were unconditionally adding /usr/lib to the rpath, making
it impossible to use the -z nodefaultlibs linker flag.  RTLD will look in
/usr/lib by default as the last priority of the library search path as
long as the object wasn't built with -z nodefaultlibs.
gcc41: remove /usr/lib from rpath

The gcc41 specs were unconditionally adding /usr/lib to the rpath, making
it impossible to use the -z nodefaultlibs linker flag.  RTLD will look in
/usr/lib by default as the last priority of the library search path as
long as the object wasn't built with -z nodefaultlibs.

Also the __DragonFly__ macro was bumped from 1 to 3.  It's supposed to
reflect the major version of DragonFly.
defaults: remove /usr/lib/gcc* from ldconfig search path

It is not necessary for ldconfig to add /usr/lib/gcc44 and /usr/lib/gcc41
directories to the default library search path.  Every binary built with
gcc41 and gcc44 embeds these paths into the DT_RPATH dynamic tag which
tells the runtime linker to look their first.  In effect, this means these
paths are potentially searched multiple times: once due to the rpath and
again due to the ldconfig hints file.  Let's do away will the redundant,
always-fails check here.

Another reason is that the gcc libraries have different versions of the
same libraries.  Surely the gcc41 version isn't preferred over the gcc44
version, but it gets searched first.  Again, let rpath take care of this
for gcc.

To update the rc.conf defaults, "make upgrade" after building world is
required.
Merge branch 'master' into gsocdrm_github
VFS accounting: do not set vp->v_pfsmp for non-nullfs mounts

* the test in _cache_setvp() was wrong and was initializing a pfs-specific
  accounting variable in vnodes for all filesystem types, possibly causing
  unnecessary work for each filesystem write operation.