[pfff/php] support for trailing comma in tuple type declaration

Summary: @override-unit-failures

Test Plan: make tests

Reviewers: jcreed, jwatzman, glevi, julienv, vsi, eletuchy

Reviewed By: eletuchy

Subscribers: zwnj

Differential Revision: https://phabricator.fb.com/D1498913

Tasks: 4896557
Merge branch 'master' of github.com:facebook/pfff
[codequery/php] add return/2

Summary:
Alex wanted that

@override-unit-failures

Test Plan: unit tests included

Reviewers: bill, eletuchy, srenfro, jcreed, alecm

Reviewed By: alecm

Differential Revision: https://phabricator.fb.com/D1511936