Our header was out-of-date with some EGL 1.5 Image-related stuff.
This fixes the new dEQP compile which relies on the entry points
being defined.

BUG=angle:901

Change-Id: Ic6ecf45c9e626e4b8e5f715f5301a9fbba295f3e
Reviewed-on: https://chromium-review.googlesource.com/244443Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>