Fixtype of declarators [C:6.7.6] [C:A.2.2].
This is a product type introduced by fty::defprod.
This corresponds to declarator in the grammar in [C]. The optional pointer that precedes the direct-declarator is a sequence of stars each optionally followed by an optional sequence of type qualifiers and attribute specifiers. We model this as a list of lists of type qualifiers and attribute specifiers: the outer list corresponds to each star, and each inner list corresponds to the type qualifiers and attribute specifiers that immediately follow the star.