pfff: support XHP comment syntax <!-- ... -->

Summary:
For UIE.
Reference: https://phabricator.fb.com/D873971

Test Plan:
unit test included
make test

Reviewers: jiaol, pieter, julienv, amenghra

Reviewed By: pieter

CC: kdelong, jdelong

Differential Revision: https://phabricator.fb.com/D875405
* tests/php/parsing/chaining2.php:
Merge branch 'master' of github.com:facebook/pfff
pfff: 'make update' in pfff/data/php_stdlib

Summary:
Update list of builtins from hphp automatically.
I used to run pfff_test -builtins_of_idl manually on each idl
but it does not scale well.

Test Plan: make test

Reviewers: jiaol, pieter, julienv, amenghra

Reviewed By: pieter

Differential Revision: https://phabricator.fb.com/D879578
* data/php_stdlib/builtins_collections.idl.php: new
* data/php_stdlib/builtins_icu_ucnv.idl.php: new
* data/php_stdlib/builtins_filter.idl.php: new
* data/php_stdlib/: update
* data/php_stdlib/facebook.php: fixed dupes