GCC 4.7 compilation fix

now builds for me on Debian-7 Wheezy 64bit

unqualified member functions in dependent base classes not found anymore.
Need to qualify either the class or the instance.

src/lib/time/control-policy.hpp

@@ -270,7 +270,7 @@ namespace mutation {
       static TI
       dontChange (TAR& target)  ///< @note: not touching the target
         {
-          return buildChangedValue(target);
+          return Link::buildChangedValue(target);
         }
     };