reduce RAM usage in tarjan algorithm via trimToSize

Author: Peter

core/src/main/java/com/graphhopper/routing/util/TarjansStronglyConnectedComponentsAlgorithm.java

@@ -123,6 +123,7 @@ private void strongConnect( int firstNode )
                     onStack.clear(node);
                 }
                 component.add(start);                
+                component.trimToSize();
                 onStack.clear(start);
 
                 components.add(component);