Merge proc.h:1.449 and kern_thread.:1.225 from HEAD to RELENG_6:

Merge proc.h:1.449 and kern_thread.:1.225 from HEAD to RELENG_6:

  Add new fields to process-related data structures:

  - td_ar to struct thread, which holds the in-progress audit record during
    a system call.

  - p_au to struct proc, which holds per-process audit state, such as the
    audit identifier, audit terminal, and process audit masks.

  In the earlier implementation, td_ar was added to the zero'd section of
  struct thread.  In order to facilitate merging to RELENG_6, it has been
  moved to the end of the data structure, requiring explicit
  initalization in the thread constructor.

Obtained from:  TrustedBSD Project