get rid of preprocessor conditional

having 2 different implementations (one for c++11 and one for c++03)
makes the code harder to maintain.

src/scripting/game_lua_kernel.cpp

@@ -96,6 +96,8 @@
 #include <boost/bind.hpp>               // for bind_t, bind
 #include <boost/foreach.hpp>            // for auto_any_base, etc
 #include <boost/intrusive_ptr.hpp>      // for intrusive_ptr
+#include <boost/range/algorithm.hpp>    // boost::copy
+#include <boost/range/adaptors.hpp>     // boost::adaptors::filtered
 #include <boost/tuple/tuple.hpp>        // for tuple
 #include <cassert>                      // for assert
 #include <cstring>                      // for strcmp, NULL
@@ -1586,11 +1588,9 @@ static int intf_find_reach(lua_State *L)
 	return 1;
 }
 
-#ifdef HAVE_CXX11
 static bool intf_find_cost_map_helper(const unit * ptr) {
 	return ptr->get_location().valid();
 }
-#endif
 
 /**
  * Is called with one or more units and builds a cost map.
@@ -1618,18 +1618,7 @@ static int intf_find_cost_map(lua_State *L)
 	}
 	else if (!filter.null())  // 1. arg - filter
 	{
-		const unit_filter ufilt(filter, resources::filter_con);
-
-		#ifdef HAVE_CXX11
-		std::vector<const unit *> matches = ufilt.all_matches_on_map();
-		std::copy_if(matches.begin(), matches.end(), std::back_inserter(real_units), &intf_find_cost_map_helper);
-		#else
-		BOOST_FOREACH(const unit * u, ufilt.all_matches_on_map()) {
-			if (u->get_location().valid()) {
-				real_units.push_back(u);
-			}
-		}
-		#endif
+		boost::copy(unit_filter(filter, resources::filter_con).all_matches_on_map() | boost::adaptors::filtered(&intf_find_cost_map_helper), std::back_inserter(real_units));
 	}
 	else  // 1. + 2. arg - coordinates
 	{