loader: bug 12992: extension and layer support

Much of layers and loader updated to work with
final extension and layer mechanism.
Not everything is working here.
diff --git a/tests/init.cpp b/tests/init.cpp
index e4396d5..9c70b98 100644
--- a/tests/init.cpp
+++ b/tests/init.cpp
@@ -105,8 +105,10 @@
         inst_info.pNext = NULL;
         inst_info.pAppInfo = &app_info;
         inst_info.pAllocCb = NULL;
+        inst_info.layerCount = 0;
+        inst_info.ppEnabledLayerNames = NULL;
         inst_info.extensionCount = 0;
-        inst_info.pEnabledExtensions = NULL;
+        inst_info.ppEnabledExtensionNames = NULL;
         err = vkCreateInstance(&inst_info, &inst);
         ASSERT_VK_SUCCESS(err);
         err = vkEnumeratePhysicalDevices(inst, &this->gpu_count, NULL);