kernel - Terminate ddb backtraces at Xfast_syscall

* Terminate ddb backtraces at Xfast_syscall to try to avoid double-faults
  from recursing into garbage.
Merge branch 'master' into gsocdrm_alter
<pthread.h>: Adjust the visibility of pthread_{get,set}stackaddr() protos.

The functions were removed from issue 7 of the specification.

http://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xsh_chap01.html
netisr: Inline netisr_cpuport() and netisr_curport()

These two functions do nothing more than just return pointer to the
element in the array.

Per our header file naming convention, put these two functions in
net/netisr2.h
netisr: Add netisr_hashport, which finds netisr msgport based on pkt hash
netisr: Add netisr_hashcpu, which maps pkt hash to cpuid
netisr: Renaming, cpufn -> hashfn; no functional changes
netisr: Fix comment
ip_demux: Remove unused udp_mpsafe_thread global variable
ip_demux: Save raw hash, instead of hash masked w/ ncpus2_mask, i.e. cpuid
toeplitz: Return raw hash

Currently only 16 bits are valid, since the key is seeded with 2 bytes.
rtadvd(8): Fix a typo in a message.
hammer2 - Major restructuring, part 3/several

* Use hammer2_chain_duplicate() to move hardlinks to common parents.

* Adjust flush algorithms, particularly when it comes to figuring out
  when we can clear the MOVED bit on a chain.

* chain RBTREE sorts on delete_tid in addition to sorting on the key.
  Add ranged searches.

  The frontend no longer modifies indirect blocks.  Instead, chains in
  the RBTREE are used to placehold both insertions and deletions.

* Stabilization pass.  (still work to do on chain refs / unmount and
  optimizing the flush).
Merge branch 'master' into gsocdrm_merger