layers: Add VK_NV_external_memory_win32 ext to PV
layers: Add VK_NV_external_memory_win32 ext to PV

Added GetMemoryWin32HandleNV function for this extension to the
parameter validation layer.

Change-Id: Ib1b870ab2b0433a19fcdca6bb6e0bffbeda74a13

KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers