Upgrade to PHP 7.2.0

Summary:
GPG keys for PHP 7.2.0 belong to Sara Golemon (pollita)
and Remi Collet (remi).

References:

• http://php.net/manual/en/migration72.php
• http://php.net/archive/2017.php#id2017-11-30-1
• http://be2.php.net/downloads.php#gpg-7.2

Test Plan:

• Build image, run phpinfo
• Rebuild nasqueron/arcanist image, run arc

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1274