[cmf] generate all builtins, even hack builtins

Summary:
the regression tests in pfff/facebook were broken because
many functions like chr() were then unknown. I am not sure
of the current status of stdlib and hack so for now I just
wanted to unbreak my tests and cmf.

Test Plan: make test now work again

Reviewers: jwatzman

Reviewed By: jwatzman

CC: bryano

Differential Revision: https://phabricator.fb.com/D1147247
[pfff] fix precedence of await

Test Plan: before/after: https://phabricator.fb.com/P4459909

Reviewers: glevi, julienv, jcreed

CC: bryano, amenghra

Differential Revision: https://phabricator.fb.com/D1137350

Task ID: 2985837
Merge branch 'master' of github.com:facebook/pfff
* find_source.ml: factorize code
* find_source.ml:
* data/php_stdlib/extra/hphp_builtins.php: fix
factorize code regarding skip_list, pull it out of all those
Graph_code_xxx.build functions, do that before
make graph works again, pass ml files to functions