MFC: revs 1.23 and 1.24
MFC: revs 1.23 and 1.24

* Replace fch{mod,own} with straight ch{mod,own} as the former cannot be used
  on socket file descriptors
* Open permissions on /var/run/devd.pipe so that any user can read devd events
  from this socket
* Enable non-blocking I/O on devd.pipe to keep clients from wedging devd.
  If a write(2) on devd.pipe would block, the client in question will be
  removed

Approved by:	re (kensmith)

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