Roll SPIRV-Tools and SPIRV-headers (June 2018) Bug: angleproject:2691 Change-Id: I754431c7cf7cdbb5b631e9db90b7c1471b5bf9ee Reviewed-on: https://chromium-review.googlesource.com/1117309 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Luc Ferron <lucferron@chromium.org> Reviewed-by: Tobin Ehlis <tobine@google.com>