- Change CURSIG() and postsig() to require that the proc lock is held   rather than grabbing it and releasing it themselves.  This allows callers   of these functions to get the lock to close race conditions. - Grab Giant around ktrace in postsig. - Count the switches performed on SIGSTOP's as involuntary context switches   in the resource usage stats.
- Change CURSIG() and postsig() to require that the proc lock is held
  rather than grabbing it and releasing it themselves.  This allows callers
  of these functions to get the lock to close race conditions.
- Grab Giant around ktrace in postsig.
- Count the switches performed on SIGSTOP's as involuntary context switches
  in the resource usage stats.

Reported by:	tegge (signal race), bde (missing csw stats)

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase