Previous to this commit, the shadowing of imported type constructors
by local type constructors was not implemented, causing misleading
error messages.

Now the comment regarding the export expansion of records matches the behaviour implemented in the frontend

This change also qualifies the names in global (top-level) declarations
although the names can only be notated unqualified in Curry. This is to
faciliate the meta-programming, for instance the retrieval of a function
declaration. In addition, primitive entities such as tuples, unit and
list constructors are qualified for the same reason.