fail and fail_bounds_checks lang items should take `&'static str` not `*u8`

[huonw]

These lang items are currently defined as

pub fn fail_(expr: *u8, file: *u8, line: uint) -> !
pub fn fail_bounds_check(file: *u8, line: uint, index: uint, len: uint) -> !

We convert the expr and file arguments to &'static str via unsafe internally, but we could just avoid this and have the compiler emit them as slices rather than C strings.

cc #12357.

[treeman]

This has been fixed, they are now

fn fail_(expr_file_line: &(&'static str, &'static str, uint)) -> !
fn fail_bounds_check(file_line: &(&'static str, uint), index: uint, len: uint) -> !

Can close this issue.