Add support for function as dictated by the Vulkan spec
for Xlib WSI (32.4.5)

Bug: b/124265819
Change-Id: I61e9ca4b34c7b57102d32ff24cecde2b9e513a5f
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/32228
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Hernan Liatis <hliatis@google.com>