Make libphutil utils.php PHP version violations statically analyzable
Ref T13249. We actually already have a function_exists() check.
We don't have a constant() check, but the next change will add one.
Test Plan: Ran unit tests. No more lint warnings.
Reviewed By: amckinley
Maniphest Tasks: T13249
Differential Revision: https://secure.phabricator.com/D20145