* pinfo.h (maybe_set_exit_code_from_windows): Renamed from set_exit_state.

* pinfo.h (maybe_set_exit_code_from_windows): Renamed from set_exit_state.
* pinfo.cc (pinfo::exit): Use renamed function.
(proc_waiter): Ditto.  Make a copy of input argument to avoid problems when
procs array is shuffled.  Flag when copy is made so that remove_proc knows when
it is safe to reshuffle.
* sigproc.cc (proc_terminate): Don't flag process_state as PID_EXITED.
(remove_proc): Wait for waiter to finish copying pinfo element before moving it
(an actual wait should be an extremely rare event).