Add 'const' on XMLDocument::DeepCopy. This make us copy const
XMLDocument being copied to another document.
diff --git a/tinyxml2.h b/tinyxml2.h
index a372b41..7b5bb0e 100755
--- a/tinyxml2.h
+++ b/tinyxml2.h
@@ -1826,7 +1826,7 @@
 

 		NOTE: that the 'target' must be non-null.

 	*/

-	void DeepCopy(XMLDocument* target);

+	void DeepCopy(XMLDocument* target) const;

 

 	// internal

     char* Identify( char* p, XMLNode** node );