This extension only actually adds an enum. The interesting behavior will
come with image and buffer memory barriers describing an ownership
transition between the real queue family and
VK_EXT_QUEUE_FAMILY_FOREIGN. Depending on the platform, this may be
nothing; may require cache maintenance operations; or may require
a copy to/from an external buffer.

Bug: b/141697747
Change-Id: Ia5b6d3027f21bb7c61143972fcb4d4cd8bc06f11
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/36728Tested-by: Chris Forbes <chrisforbes@google.com>
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>