Fix bug on paramenter default value : undefined constant

Signed-off-by: Kevin Nguyen <k.nguyen@thecodingmachine.com>
Merge branch '2.0' of git://github.com/thecodingmachine/mouf into 2.0

Conflicts:
	src/Mouf/Reflection/MoufReflectionParameter.php

Signed-off-by: Kevin Nguyen <k.nguyen@thecodingmachine.com>