Merge a small amount of remaining "libphutil/" code with Phabricator, break libphutil dependency

Summary: Ref T13395. Moves a small amount of remaining "libphutil/" code into "phabricator/" and stops us from loading "libphutil/".

Test Plan: Browsed around; there are likely remaining issues.

Maniphest Tasks: T13395

Differential Revision: https://secure.phabricator.com/D20981