Fix the ArcanistXHPASTLinter single quote rule.

Summary: Previously, the ArcanistXHPASTLinter was suggesting that "\1" be written as '\1', which is incorrect. Therefore, I ensured that all of the cases listed in the PHP documentation were handled correctly.

Test Plan: arc unit

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9182