Support tuples in match arms

[klinvill]

It would be nice to have support for pattern matching against tuples. In particular, I'd like to be able to write something like:

    #[define]
    fn equiv_options<T>(v1: &Option<T>, v2: &Option<T>) -> bool {
        match (v1, v2) {
            (Option::<T>::Some(inner1), Option::<T>::Some(inner2)) => true,
            (Option::<T>::None, Option::<T>::None) => true,
            _ => false,
        }
    }

but currently such a match pattern would require instead writing:

    #[define]
    fn equiv_options<T>(v1: &Option<T>, v2: &Option<T>) -> bool {
        match v1 {
            Option::<T>::Some(inner1) => {
                match v2 {
                    Option::<T>::Some(inner2) => true,
                    Option::<T>::None => false,
                }
            },
            Option::<T>::None => {
                match v2 {
                    Option::<T>::Some(inner2) => false,
                    Option::<T>::None => true,
                }
            }
        }
    }

Of course, writing my desired match statement with the wildcard also requires #3 to be added, but support for matching against tuples should be added as well to allow for writing the match arms based on semantic meaning (e.g. I'd like to be able to group the true arms together and the false arms together).