using `good` function (compatible with recent version of g++)

src/camel/Engine.cc

@@ -102,7 +102,8 @@ Engine::get(const std::string& key){
     planck_assert(key.substr(key.size()-1,1)==")",key+": keyword not finishing with )");
     var=key.substr(0,index);
     istringstream isNum(key.substr(index+1,key.size()-index-2));
-    planck_assert(isNum >> z,key+": Engine cannot decode z value in keyword");
+    isNum >> z;
+    planck_assert(!isNum.good(),key+": Engine cannot decode z value in keyword");
   }
   if (var=="z_drag")  return  z_drag();
   else if (var=="rs_drag") return  rs_drag();