Throw error when overriding properties without getter/setter.

[jasssonpet]

Throw error when overriding a (non-readonly) native property without both a getter/setter function:

@interface TNSBaseInterface : NSObject
@property int baseProperty;
@end

TNSBaseInterface.extend({
    get baseProperty() {
        console.log('get');
        return this.super.baseProperty;
    },
    // set baseProperty(value) {
    //     console.log('set');
    //     this.super.baseProperty = value;
    // },
});

[fealebenpae]

👍 It is right to protect this condition with an error so that the runtime doesn't crash.