* Move checking the validity of a derived class with no constructor
from evlauation to binding (verification). Furthermore, make it
a verification error instead of an assert, and make the checking
complete (i.e., don't just check for the existence of a base class,
also check for the existence of a ctor, recursively).
* Refactor the constructor accessor out of the evaluator and make it
a method, Ctor, on the Function abstraction.
* Add a recursive Module population case to property initialization.
* Only treat the top-most frame in a module's initializer as belonging
to the module scope. This avoids interpreting block scopes within
that initializer as belonging to the module scope. Ultimately, it's
up to the language compiler to decide where to place scopes, but this
gives it more precise control over module scoping.
* Assert against unsupported named/star/keyword args in CocoPy.