Add version check whitelists for constants to the version compatibility lint rule

Summary: Ref T13249. We currently allow if (function_exists('X')) { X(); } but not if (defined('X')) { X; }. Allow the latter.

Test Plan: See D20145, which linted clean with this patch in place.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13249

Differential Revision: https://secure.phabricator.com/D20146