NetPlay: add a Common/ENetUtil namespace

Move WakeupThread in it

Source/Core/Common/ENetUtil.h

@@ -0,0 +1,15 @@
+// Copyright 2015 Dolphin Emulator Project
+// Licensed under GPLv2
+// Refer to the license.txt file included.
+//
+#pragma once
+
+#include <enet/enet.h>
+#include "Common.h"
+
+namespace ENetUtil
+{
+
+void WakeupThread(ENetHost* host);
+
+}