Bug: angleproject:2482

Rolling Vulkan validation code forward to HEAD of master as of 4/18/18
morning. Disable Vulkan from the ANGLE build until ANGLE lands in
Chromium. After that second part of roll will be submitted.

This LVL update includes reg.py script fixes for a number of build
warnings as well as a validation fix for vkCmdClearAttachments() in
secondary cmd buffer.

Change-Id: I7f8100f5b656d86caf8f4b5dee61a733a35b7869
Reviewed-on: https://chromium-review.googlesource.com/1016860Reviewed-by: Jamie Madill <jmadill@chromium.org>