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/driver_gen.h b/vulkan/libvulkan/driver_gen.h
index 0228ef2..167f88c 100644
--- a/vulkan/libvulkan/driver_gen.h
+++ b/vulkan/libvulkan/driver_gen.h
@@ -38,6 +38,7 @@
         KHR_android_surface,
         KHR_surface,
         KHR_swapchain,
+        GOOGLE_display_timing,
 
         EXTENSION_CORE,  // valid bit
         EXTENSION_COUNT,