Parse a direct declarator.
(parse-direct-declarator parstate) → (mv erp dirdeclor span new-parstate)
A direct declarator always starts with either an identifier or a parenthesized declarator, and continues with zero or more array or function constructs that augment the declarator. First we parse the initial identifier or parenthesized declarator, then we call a separate function to parse the zero or more array or function constructs.