Idea: Allow loop to take parameters

[porky11]

Blocks will take parameters, for example by specifying them using with before them.

For example now a factorial would look like this:

fn factorial(x: i32)
{
    var result: i32 = 1;
    var i = x;

    {
        if i == 0
            goto return;
        result = result * i;
        i = i - 1
        loop;
    }
    
    return: result
}

When loop takes parameters, it could look like this:

fn factorial(x: i32)
{
    with result: i32 = 1, i = x;
    {
        if i == 0
            goto return;
        loop result * i, i - 1;
    }
    
    return: result
}

(I don't think, these with-parameters should be exposed after the loop, but if return parameters are not exposed, but then we would need other features like #3 to make it useful)