Adds prerequisite_type to the list of prerequisites of interface_type.
This means that any type implementing interface_type must also implement prerequisite_type. Prerequisites can
be thought of as an alternative to interface derivation (which GType doesn't support). An interface can have at most one instantiatable
prerequisite type.
| prerequisite_type |
Type value of an interface or instantiatable type |
| interface_type |
Type value of an interface type |