CppCheck linter

Summary:
Lints cpp code using the cppcheck static linter. This linter needs to
be downloaded and built from http://cppcheck.sourceforge.net/

Test Plan: Used it on a few files.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4353