[test] Add a test that checks for valid copyright and licenses

[test] Add a test that checks for valid copyright and licenses

Tests all `.h`, `.c`, `.py`, and `Makefile` files for valid copyright
and license lines. Excludes a small number of exceptions (threading, and
divsufsort).

* Copyright does not contains `present`
* Copyright contains `Facebook, Inc`
* Copyright contains the current year
* License contains exactly the lines we expect