- Reorganize osigstack() to do the copyin first, grab the proc lock once,   do all the various sigstack dances, unlock the proc lock, and finally do   the copyout.  This more closely resembles the behavior of   kern_sigaltstack() and closes a small race. - Remove Giant from osigstack as it is no longer needed.
- Reorganize osigstack() to do the copyin first, grab the proc lock once,
  do all the various sigstack dances, unlock the proc lock, and finally do
  the copyout.  This more closely resembles the behavior of
  kern_sigaltstack() and closes a small race.
- Remove Giant from osigstack as it is no longer needed.

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