Device matching by LUID not specified

`VkPhysicalDeviceIDProperties` descriptions say:

> `deviceUUID` and/or `driverUUID` **must** be used to determine whether a particular external object can be shared between driver components, where such a restriction exists as defined in the compatibility table for the particular object type: [...]

It should be possible to match by LUID as well, and the issue 6 of `VK_KHR_external_memory_capabilities` does say so:

> To allow correlating with Direct3D devices, a device LUID is added that corresponds to a DXGI adapter LUID. A driver ID is not needed for Direct3D because mismatched driver component versions are not a currently supported configuration on the Windows OS.

Something to this effect should be added to the normative parts of the specification.

Start by reading the VkPhysicalDeviceIDProperties descriptions and issue 6 of VK_KHR_external_memory_capabilities, then compare their requirements for deviceUUID, driverUUID, and device LUID. Update the normative specification text so LUID matching is addressed consistently with the Direct3D compatibility rationale.

Written by the indexing model from the issue text.