Extends are not handled properly

[Martin Sjölund]

{{{class B

extends A;
extends A;
extends A;
extends A;
Integer i;

end B;
class A

extends B;
extends B;
extends B;
... x300.000
extends B;

end A;
}}}

Expected output:
{{{class A

Integer i;

end A;}}}

A smart implementation would keep a list of all classes(+modifications) it has currently inherited (start-value of course includes itself).

[Per Östlund]

The new frontend gives an error "extends A causes an instantiation loop".