In Diviner, parse "abstract" and "final" in PHP classes, interfaces and methods
Summary: Ref T988. Adds support for the "abstract" and "final" keywords in the atomizer.
Test Plan: Looked at abstract/final stuff.
Reviewers: btrahan, chad
Reviewed By: chad
Maniphest Tasks: T988
Differential Revision: https://secure.phabricator.com/D6850