If we have to increase nfds because startup_pipe[0] is above any of the
descriptors passed in the fd_sets, we also need to add 1 to nfds since
select takes highest FD number plus one. bz#3345 from yaroslav.kuzmin
at vmssoftware.com.
On the second and subsequent calls to pselect the notify_pipe was not
added to the select readset, opening up a race that om G. Christensen
discovered on multiprocessor Solaris <=9 systems.
Also reinitialize notify_pipe if the pid changes. This will prevent a
parent and child from using the same FD, although this is not an issue
in the current structure it might be in future.
This is basically the existing notify_pipe kludge from serverloop.c
moved behind a pselect interface. It works by installing a signal
handler that writes to a pipe that the select is watching, then calls
the original handler.
The select call in serverloop will become pselect soon, at which point the
kludge will be removed from thereand will only exist in the compat layer.
Original code by markus, help from djm.
