Add for statement and range function; New register_box_fn for functions returning Box<dyn Any> (which should not be boxed again); Register standard utility functions in library (e.g. print, string concat).

src/any.rs

@@ -76,7 +76,7 @@ impl Clone for Box<dyn Any> {
 
 impl fmt::Debug for dyn Any {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.pad("Any")
+        f.pad("?")
     }
 }