layers: Change include order of loader platform.

This fixes a bug where on Windows, windows.h would include
winsock.h before winsock2.h, causing numerous warnings.

Change-Id: I8eba1497385dcee6ebb201c74fe48268e6663b9c
diff --git a/layers/unique_objects.h b/layers/unique_objects.h
index b8effcf..3fbf54e 100644
--- a/layers/unique_objects.h
+++ b/layers/unique_objects.h
@@ -25,14 +25,14 @@
  * Author: Tobin Ehlis <tobine@google.com>
  */
 
+#include "vk_loader_platform.h"
+#include "vulkan/vulkan.h"
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <inttypes.h>
 
-#include "vulkan/vulkan.h"
-#include "vk_loader_platform.h"
-
 #include <vector>
 #include <unordered_map>