Moved #includes in TGLContext.h inside headerguard

Signed-off-by: Vassil Vassilev <vvasilev@cern.ch>

graf3d/gl/inc/TGLContext.h

 // @(#)root/gl:$Id$
 // Author:  Timur Pocheptsov, Jun 2007
 
-#include <utility>
-#include <list>
-
 /*************************************************************************
  * Copyright (C) 1995-2004, Rene Brun and Fons Rademakers.               *
  * All rights reserved.                                                  *
@@ -15,7 +12,9 @@
 #ifndef ROOT_TGLContext
 #define ROOT_TGLContext
 
+#include <list>
 #include <memory>
+#include <utility>
 
 class TGLContextIdentity;