Missing include, preventing build on VS2012

git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@799 fdac6126-5c0c-442c-9429-916003d36597

src/OpenMesh/Core/IO/reader/BaseReader.hh

@@ -58,6 +58,7 @@
 #include <iostream>
 #include <string>
 #include <cctype>
+#include <functional>
 
 // OpenMesh
 #include <OpenMesh/Core/System/config.h>