dwrap5<R> method
Binds a cwraped C function taking 5 arguments and returning a plain
(non-struct) value.
R determines the JS->Dart return conversion applied on every call
(see _conv); use void if the C function returns nothing.
Implementation
WF5<R> dwrap5<R>(String name) {
final f = _wn(name, 5);
final c = _conv<R>();
return (a1, a2, a3, a4, a5) => c(f.run([a1, a2, a3, a4, a5]));
}