EGL: Entrypoint and autogen for EGL_KHR_reusable_sync Add entry point eglSignalSync Update autogen files Test: angle_deqp_egl_tests --deqp-case=dEQP-EGL.functional.reusable_sync.* Bug: angleproject:5168 Change-Id: I47afa4010c533096b4c56e9b3ab6eddc1944b83e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2472998 Commit-Queue: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jeff Vigil <j.vigil@samsung.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>