Add array method dereference support to xhpast.

Summary: Adds support for array method dereferencing, e.g. $foo->bar()[0]. Bumps XHPAST version. Ref T4334.

Test Plan: Wrote two failing unit tests for language parsing abilities using the specific errors mentioned in T4334. Hacked away at the parser importing bits from Zend's zend_language_parser.y until they passed.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T4334

Differential Revision: https://secure.phabricator.com/D8611