* lang_php/analyze/foundation/unsugar_php.ml: comment
* tests/php/scheck/namespaces.php: test
unsugar_php: better handle namespace (fix for fbt_exractor)

Summary:
One file in www is now using namespace (flib/search/elasticsearch/ElasticaShim.php) which caused some troubles to unsugar_php.ml.
This diff fixes that.

Test Plan:
./fbt_extractor.opt -tasks 32 ~/www/
now works

Reviewers: pieter, mmachedon, michalburger1

Reviewed By: pieter

Differential Revision: https://phabricator.fb.com/D970039
* tests/php/scheck/namespaces_php: skip for now