Function merge_sort 

pub fn merge_sort(data: &[i64]) -> Vec<i64>

Merge sort implementation on a mutable slice.

Returns a sorted copy of the input using stable merge sort.

Example

let sorted = merge_sort(&[3, 1, 4, 1, 5, 9, 2, 6]);
assert_eq!(sorted, vec![1, 1, 2, 3, 4, 5, 6, 9]);