Update on strict funcs

[xigoi]

You can think of
    
    
    func f(x: var X): Y
    var x: X
    let y = f(x)
    
    
    Run

as sugar for
    
    
    func f(x: X): tuple[X, Y]
    var x: X
    let (newx, y) = f(x)
    x = newx
    
    
    Run