Use PhutilXHPASTBinary methods
Summary: Use PhutilXHPASTBinary methods instead of xhpast_parse functions. Depends on D11517.
Test Plan: N/A, this is a direct swap.
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: Korvin, epriestley
Differential Revision: https://secure.phabricator.com/D11614