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>
