Fix the issue with variant/record short field types

[seniorjoinu]

As described in #20

variant { A; B; C }

and

type A = int;
type B = int;
type C = int;

record { A; B; C }

In the first example A, B and C are name values of variants. After parsing they go into IDLFieldType(variantName, IDLType.Primitive.Null). In the second example A, B and C are types of positional record fields. After parsing they go into IDLFieldType(null, recordFieldType).

Which is done incorrect right now.