* pinfo.cc (proc_waiter): Zero wait_thread in child to avoid races with process

termination.
* cygthread.cc (cygthread::terminate): Clumsily detect when h has gone away and
attempt no further action.

winsup/cygwin/pinfo.cc

@@ -763,6 +763,7 @@ proc_waiter (void *arg)
     }
 
   sigproc_printf ("exiting wait thread for pid %d", pid);
+  vchild.wait_thread = NULL;
   _my_tls._ctinfo->release ();	/* return the cygthread to the cygthread pool */
   return 0;
 }