loader: Cleanup 1.0.25 extension work

Remove adding extensions from being exported from loader by
default.  Add in logic to only export entry points if extensions
are enabled.

Change-Id: I56e0c673925869e0d4482ee401ea19e43a05267f
diff --git a/loader/extensions.h b/loader/extensions.h
index bbccc17..c84fd86 100644
--- a/loader/extensions.h
+++ b/loader/extensions.h
@@ -23,11 +23,14 @@
 #include "loader.h"
 
 bool extension_instance_gpa(struct loader_instance *ptr_instance,
-    const char *name, void **addr);
+                            const char *name, void **addr);
 
 void extensions_create_instance(struct loader_instance *ptr_instance,
                                 const VkInstanceCreateInfo *pCreateInfo);
 
+void extensions_create_device(struct loader_device *dev,
+                              const VkDeviceCreateInfo *pCreateInfo);
+
 // Definitions for the VK_NV_external_memory_capabilities extension
 
 VKAPI_ATTR VkResult VKAPI_CALL