GLES3: Auto-generate entry points source. Lots of incidental fixes to formatting and naming. Adds specific default return type overloads for ClientWaitSync and GetUniformBlockIndex. BUG=angleproject:1309 Change-Id: Id67cbc0b19fc2cb94c859ab8390f1ff36b1bbd25 Reviewed-on: https://chromium-review.googlesource.com/637203 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>