typedef __mpz_struct mpz_t[1];

Cgo generates:

	type _C_int int32
	type _C_mp_limb_t uint64
	type _C___mpz_struct struct {
		_mp_alloc _C_int;
		_mp_size _C_int;
		_mp_d *_C_mp_limb_t;
	}
	type _C_mpz_t [1]_C___mpz_struct

and then replaces each occurrence of a type C.xxx with _C_xxx.

If xxx is data, cgo arranges for C.xxx to refer to the C variable,
with the type translated as described above.  To do this, cgo must