Allow closing tags in files containing HTML

Summary: Ref T8742. PHP files which contain inline HTML should be allowed to use PHP closing tags (?>). This is in accordance with PSR-2 guidelines.

Test Plan: Updated unit tests.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin

Maniphest Tasks: T8742

Differential Revision: https://secure.phabricator.com/D13794