Add GL_EXT_copy_image extension entry points Bug: angleproject:3593 Change-Id: I6d3a55a3112f5f9b20ef33c859a60b2952bfbc2f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2444209 Commit-Queue: Mohan Maiya <m.maiya@samsung.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>