Add password_* functions to extension functions list

Summary: These are technically added in PHP 5.5.0 mainline, not an extension, but the two are effectively equiavlent.

Test Plan: o.O

Reviewers: btrahan, dctrwatson

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D8280
Merge branch 'master' of http://github.com/facebook/arcanist