Fix child process leaking, solution given by upstream
see https://code.activestate.com/lists/perl-poe/5008/
Index: t/90_regression/rt56417-wheel-run.t
--- t/90_regression/rt56417-wheel-run.t.orig
+++ t/90_regression/rt56417-wheel-run.t
@@ -93,6 +93,8 @@ sub _wheel_child {
 }
 
 sub _stop {
+	use POSIX ":sys_wait_h";
+	1 while waitpid(WNOHANG, -1) > 0;
 	pass("we sanely died (" . $_[HEAP]->{type} . ")");
 	return;
 }