egl_angle_ext.xml: add missing enums and typedefs This is necessary for a loader like GLAD to generate a correct egl.h header with ANGLE extensions. Bug: angleproject:7193 Change-Id: Id3f07ffee216890418b202520fccff7ccfcaa6dd Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3582273 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>