* lang_php/analyze/checker/unit_checker_php.ml: fix
pfff: support native function declaration

Summary:
make test was failing on cmf because the new PHP standard library
contains native function declaration with a new syntax.

Test Plan: make test

Reviewers: pieter, jdelong, andrewparoski

Reviewed By: jdelong

CC: julienv, amenghra, joelm

Differential Revision: https://phabricator.fb.com/D965694
* lang_php/analyze/foundation/unsugar_php.ml: undo pieter
* lang_php/analyze/foundation/controlflow_build_php.ml: undo pieter
* lang_php/analyze/checker/check_variables_php.ml: undo pieter