sgrep: allow new X(...) to match new X;

Summary: vlad needs that to factorize rules in SgrepLint

Test Plan:
unit test included
$ ./sgrep -test

Reviewers: pieter, vshubin, zoel

Reviewed By: pieter

CC: julienv, amenghra

Differential Revision: https://phabricator.fb.com/D765374
* demos/: CEs