Fixed compiler warning for x64 builds.
diff --git a/tinyxml2.cpp b/tinyxml2.cpp
index 510de38..a6ec20a 100755
--- a/tinyxml2.cpp
+++ b/tinyxml2.cpp
@@ -1684,7 +1684,7 @@
         return _errorID;

     }

 

-	int delta = p - start;	// skip initial whitespace, BOM, etc.

+    ptrdiff_t delta = p - start;	// skip initial whitespace, BOM, etc.

     ParseDeep( _charBuffer+delta, 0 );

     return _errorID;

 }