Compiler: Don't reference inherited prototypes.
Having local references to inherited prototype functions is not
useful, as they can never become anything else than a prototype.
It also confuses code that uses mixins and attempts to use the
anonymous inherit specifier to access the base implementation
in one inherited class when there's a corresponding prototype
in another inherited class, in which case both functions were
returned. This typically caused "Calling undefined function.".
As a bonus this also improves code generation somewhat.