loader: Add support for NV instance extension

Added vkGetPhysicalDeviceExternalImageFormat API from the
VK_NV_external_memory_capabilities extension to the loader.

Change-Id: Ib87df7bae333d7944a4e181556bc2f99e1e19416
diff --git a/loader/loader.h b/loader/loader.h
index 5a1515e..ce78d4d 100644
--- a/loader/loader.h
+++ b/loader/loader.h
@@ -209,6 +209,8 @@
     PFN_vkGetPhysicalDeviceSurfaceFormatsKHR GetPhysicalDeviceSurfaceFormatsKHR;
     PFN_vkGetPhysicalDeviceSurfacePresentModesKHR
         GetPhysicalDeviceSurfacePresentModesKHR;
+    PFN_vkGetPhysicalDeviceExternalImageFormatPropertiesNV
+        GetPhysicalDeviceExternalImageFormatPropertiesNV;
 #ifdef VK_USE_PLATFORM_WIN32_KHR
     PFN_vkGetPhysicalDeviceWin32PresentationSupportKHR
         GetPhysicalDeviceWin32PresentationSupportKHR;