Fixtype of Java values [JLS14:4], excluding extended-exponent values [JLS14:4.2.3].
This is a sum-of-products (i.e., union) type, introduced by fty::defflexsum.
To avoid a conflict with value, we prefix value with j for the fixtype of Java values, and, for consistency, we do the same for recognizer, fixer, and equivalence.
