Fixtype of object declarations [C:6.7].
This is a product type introduced by fty::defprod.
These are declarations for objects. [C] does not have a separate syntactic category for them, but in our abstract syntax it is useful to differentiate them from other kinds of declarators.
For now we define an object declaration as consisting of a storage class specification sequence, a type specification sequence, an object declarator, and an optional initializer.
For now we model no type qualifiers, no function specifiers, and no alignment specifiers.