Undeprecate wesnoth.highlight_hex()

wesnoth.select_hex has problems with simply highlighting units without displaying
their movement range. If you set its third argument to false, the unit gets
selected, but no hex cursors appears around it. Using this allows us to simply
highlight a location with the hex cursor, independent of unit presence (select_hex
works funny if no unit is present).

src/scripting/game_lua_kernel.cpp

@@ -1175,26 +1175,18 @@ int game_lua_kernel::intf_shroud_op(lua_State *L, bool place_shroud)
  */
 int game_lua_kernel::intf_highlight_hex(lua_State *L)
 {
-	ERR_LUA << "wesnoth.highlight_hex is deprecated, use wesnoth.select_hex" << std::endl;
-
 	if (!game_display_) {
 		return 0;
 	}
 
 	int x = luaL_checkinteger(L, 1) - 1;
 	int y = luaL_checkinteger(L, 2) - 1;
 	const map_location loc(x, y);
+	if(!map().on_board(loc)) return luaL_argerror(L, 1, "not on board");
+
 	game_display_->highlight_hex(loc);
 	game_display_->display_unit_hex(loc);
 
-	unit_map::const_unit_iterator i = board().units().find(loc);
-	if(i != board().units().end()) {
-		game_display_->highlight_reach(pathfind::paths(*i, false,
-			true, teams().front()));
-			/// @todo: teams().front() is not always the correct
-			///        choice for the viewing team.
-	}
-
 	return 0;
 }