Stubbed implementation of VK_GOOGLE_display_timing extension.

This provides the header changes and most of the "boilerplate" changes to add
the VK_GOOGLE_display_timing extension to Vulkan.  Future changes will modify
and integrate with the Surface, FrameEvents, and SurfaceFlinger code.

Test: Manually tested that existing apps won't tickle the new-extension paths.

Change-Id: Iec46b1cab4b2561702ebac9a4ae7587584793192
diff --git a/vulkan/libvulkan/api_gen.h b/vulkan/libvulkan/api_gen.h
index 7f8d274..918c1f5 100644
--- a/vulkan/libvulkan/api_gen.h
+++ b/vulkan/libvulkan/api_gen.h
@@ -177,6 +177,8 @@
     PFN_vkGetSwapchainImagesKHR GetSwapchainImagesKHR;
     PFN_vkAcquireNextImageKHR AcquireNextImageKHR;
     PFN_vkQueuePresentKHR QueuePresentKHR;
+    PFN_vkGetRefreshCycleDurationGOOGLE GetRefreshCycleDurationGOOGLE;
+    PFN_vkGetPastPresentationTimingGOOGLE GetPastPresentationTimingGOOGLE;
     // clang-format on
 };