Fixtype of structure declarations [C:6.7.2.1] [C:A.2.2].
This is a tagged union type, introduced by fty::deftagsum.
This corresponds to struct-declaration in the grammar of [C]. Despite its name in the grammar and in this fixtype, this applies to both structures and unions; in fact, it is not a declaration of a structure, but instead it is a declaration of a member of a structure or union. So something like member-declaration would be a better name for this grammar nonterminal, but our fixtype name reflects the current grammar.
As a GCC extension, we include the possibility that
a member declaration starts with
the
As a GCC extension, we include a possibly empty list of attribute specifiers, which come after the declarator (cf. the grammar)