Fix ceylon/ceylon-compiler#1561 (+ test)

The fix: in addition to the existing `largerThan(Type other)` and `static largerThan(native value, Type other)`, a `static largerThan(native value, native other)` was also needed (`native` being `long`, `double`, `int`, `java.lang.String` and `Type` being `Integer`, `Float`, `Character`, `String` respectively).

Also, the order of the four `largerThan` methods pairs was the exact reverse of the order of the other method pairs (always first `@Override`, then `static` – for the three other methods, always first `static`, then `@Override`). I’ve switched them around so now the order is always `(native,Type)`, `(native,native)`, `(Type)`.