Vulkan: Support multiple vertex outputs. This is a bit of a hack, similar to how D3D11 works. We need to write output locations in the GLSL shader before we send them to glslang, so we wait until the link call, then string-replace some hard-coded identifeir code to the attribute location determined by ANGLE. This CL also fills in some of the vertex format conversion tables in formatutilsvk.cpp. BUG=angleproject:2167 Change-Id: I2424d0d990bdbcd831a4dd130e61e87d8f8f479f Reviewed-on: https://chromium-review.googlesource.com/677555 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Frank Henigman <fjhenigman@chromium.org>