Unbound fixes #2

Summary: Me again, sorry! So after the last issue discussion, here I am adding hhi unbounds manually when I encounter them.

- Added constants to file, json, mb, and a few string modules
- Added finfo module
- Added lots of reflection stuff
Closes https://github.com/facebook/hhvm/pull/3726

Reviewed By: @jwatzman

Differential Revision: D1550354