Fix an issue mocking classes w/ traits

if a trait's method declaration fell at the wrong line number, it'd cause a syntax error, due to the random injection of the transformer into the parent class, when we thought we were injecting into the trait's file.

note that this didn't always happen, because of the way the strpos/substr seek works — it only happened when a trait's method's line number appeared in an appropriate place in the parent class

methods from traits show the same class name as the including class:
https://bugs.php.net/bug.php?id=64963
http://mouf-php.com/blog/php_reflection_api_traits

closes Codeception/AspectMock#12