Prototype with intermediary not converted to class

[github-nilsson]

function A() {}
A.prototype.func = A_func;
function A_func() { return 5; }

confuses lebab and produces

1:  warning  Function A looks like class, but has no prototype  (class)
3:  warning  Function A_func looks like class, but has no prototype  (class)
function A() {}
A.prototype.func = A_func;
function A_func() { return 5; }

instead of the expected

class A {
  func() { return 5; }
}

[nene]

Yeah, this code is a more tricky case to transform, e.g. one would need to check that A_func is not referenced anywhere else in the code.