* signal.cc (_pinfo::kill): Return success on kill(0) only if pid exists or is

in PID_EXITED state.  Report pid 0 when pid does not exist rather than pid -1.
Make debug output reflect actual function call.
* sigproc.cc (stopped_or_terminated): Set process state to reaped when we've
finished waiting for it.
* include/sys/cygwin.h (PID_REAPED): New enum.

winsup/cygwin/sigproc.cc

@@ -1041,6 +1041,7 @@ stopped_or_terminated (waitq *parent_w, _pinfo *child)
     }
   else
     {
+      child->process_state = PID_REAPED;
       w->status = (__uint16_t) child->exitcode;
 
       add_rusage (&myself->rusage_children, &child->rusage_children);