Upgrade to PHP 7.1.1

Summary:
This version uses a new GPG key, belonging to Joe Watkins.

Reference:

• http://php.net/gpg-keys.php
• http://php.net/ChangeLog-7.php#7.1.1

http://php.net/gpg-keys.php

Test Plan: dereckson

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D867