Docstring ambiguity

Hello!

I see that lambdas may have docstrings included as their first expression, as in Common Lisp and Emacs Lisp:

```scheme
(define g (lambda () "one" -1))
lips> (help g)
one
```

But define may also include docstrings, as an extra argument:

```scheme
lips> (define x 10 "two")
lips> (help x)
two
```

But... Then I cold also try to include a docstring inside a lambda, and define it as the value of a a variable with a different docstring:

```scheme
lips> (define f (lambda () "some docstring" -1) "a different docstring")
lips> (help f)
some docstring
```

Perhaps a warning could be issued in this case? When defining `f`, LIPS could warn the user that "the value is a procedure that already has a docstring"?