Added small Vulkan unit tests:
1) Checks that all API functions are present
2) Verifies a few Physical Device properties

The tests are currently only for Visual Studio,
but should be easily ported to other platforms,
as the code is similar to the GLES unit tests.

Change-Id: Idb45d26734be80e352ba91544e6331c1192f9f3e
Reviewed-on: https://swiftshader-review.googlesource.com/c/21648Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>