Install PHP common extensions

Summary:
This change installs extensions required by Arcanist, PHPUnit,
MediaWiki (hello intl), Zed (hello WDDX) or Espace Win (hello SOAP).

This encompass a fairly standard set of extensions
and should be comprehensive.

Test Plan: Run arc

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1086