Update egl.h from khronos source.
Update egl.h from khronos source.

Our header was out-of-date with some EGL 1.5 Image-related stuff.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/244443
Reviewed-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>
Tested-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

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