Don't eat whitespace after T_OPEN_TAG
Summary: Currently the scanner eats whitespace after <?php but not after <?. This means that <?php tokenises to T_OPEN_TAG (see https://secure.phabricator.com/xhpast/view/853/) whereas <? tokenises to T_OPEN_TAG, T_WHITESPACE (see https://secure.phabricator.com/xhpast/view/854/).
Test Plan:
Reviewers: epriestley, Blessed Reviewers
Reviewed By: epriestley, Blessed Reviewers
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D13890