Implement parsing of namespaces in class names included from include pat...

Fix issue #3418 when parsing the class name in autoload() in YiiBase. This bug surfaced when PHPUnit was updated. Every time you would try to run a test, it would say:

PHP Warning:  include(PHPUnit_Extensions_Story_TestCase.php): failed to open stream: No such file or directory in... (path/to/SOME_INCLUDED_PATH)