SI-6666 Restrict hidden `this` access in super calls.

Detect when classes (user provided, or compiler generated)
local to a super constructor argument would require premature
access to the in-construction instance. The same restriction
applies for classes and objects; for objects, the premature
access would by via the static MODULE$ field, which would
be null.

Communicate this with a nicely positined error.

A residual error, has been lodged as SI-6997.