Only pass args if there is a constructor
Ensures consistent behaviour across 5.9-SERIES and 6.0-SERIES

PHP reflection behaves differently, stricter, here, than the
runtime itself:

class Thing { }

new Thing();                         // Works
new Thing(1, 2, 3);                  // Works

$class= new ReflectionClass("Thing");
$class->newInstance();               // Works
$class->newInstance(1, 2, 3);        // Exception

Although the stricter way is actually better - it lets the
programmer spot errors more quickly, I believe reflection
should work consistent with the runtime

See also xp-framework/core#5