We were missing several header includes necessary for GCC. Also our
static assert macro had a bug, preventing us from using the same
assert in multiple places.

BUG=angle:568

Change-Id: I01bcdef033a9380f436cbf4bd2a9f11b1553887c
Reviewed-on: https://chromium-review.googlesource.com/195471Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>