Add gvr_is_feature_supported()

A new gvr function gvr_is_feature_supported() was added in
https://critique.corp.google.com/#review/145712807.

Implement the function to bring our gvr library up to date.

Bug: 34742071
Test: Confirmed I can once again load TreasureHunt built from google3.
Change-Id: Ib6a9802812a514ee54564f8572be9f6f4820ed01