[2347] Add missing <functional> include

This seems to be required on certain platforms (Visual Studio 2012) to
use std::bind1st, std::not_equal_to, etc. On other platforms, it may
have been transitively included.

src/lib/util/range_utilities.h

@@ -17,6 +17,7 @@
 
 #include <stdlib.h>
 #include <algorithm>
+#include <functional>
 
 // This header contains useful methods for conduction operations on
 // a range of container elements. Currently the collection is limited,