Add support for pattern bindings in function arguments and perf improvements

[udoprog]

You can now use panicking pattern bindings in functions and closures:

fn foo((a, b): #{c, d}) {
    (a + b) / (c + d)
}

pub fn main() {
    let a = (3, 1);
    let b = #{c: 1, d: 7};
    foo(a, b)
}

Also added a few performance improvements leading to this result:

The big points are:

• More variable folding leading to less copies (all though return of investment of this is lower)
• A dedicated instruction for advancing iteration (5aa6d77).