loader: Update the loader to 1.0.39

Add new extensions for 1.0.39.  Also, updated layers to include
minimal set of functionality for 1.0.39 extensions. Extensions include:
 - VK_KHR_get_physical_device_properties2
 - VK_KHR_shader_draw_parameters
 - VK_EXT_direct_mode_display
 - VK_EXT_display_surface_counter
 - VK_EXT_display_control

Also, redo the LoaderAndLayerIf document.

Change-Id: I10412086da7a798afe832a3892e18f606259b5af
diff --git a/layers/vk_layer_table.cpp b/layers/vk_layer_table.cpp
index d9ec3c5..bc9062e 100644
--- a/layers/vk_layer_table.cpp
+++ b/layers/vk_layer_table.cpp
@@ -155,6 +155,10 @@
 
     layer_init_instance_dispatch_table(instance, pTable, gpa);
 
+    // Setup func pointers that are required but not externally exposed.  These won't be added to the instance dispatch table by
+    // default.
+    pTable->GetPhysicalDeviceProcAddr = (PFN_GetPhysicalDeviceProcAddr)gpa(instance, "vk_layerGetPhysicalDeviceProcAddr");
+
     return pTable;
 }