src/c-types-impl.lisp (intern-c-type): Canonify class and initargs.

src/c-types-impl.lisp (intern-c-type): Canonify class and initargs.

Make sure the class and initargs are canonical before probing the
`*c-type-intern-map*'.

  * The class should ideally be represented by name.

  * The initargs should be in ascending order by keyword name.

In particular, this fixes a bug where `qualify-c-type' erroneously
returns a fresh type when asked to attach an empty list of qualifiers to
an already-interned type.