"Old school" error mode is now missing information first/second borrow

[sophiajt]

From #33240 (comment):

Using nightly (rustc 1.10.0-nightly (e0fd34b 2016-05-09)) on this snippet https://is.gd/jP3UYZ has less helpful error messages than stable when not using RUST_NEW_ERROR_FORMAT? E.g.

x.rs:4:15: 4:16 error: cannot borrow `a` as mutable more than once at a time [E0499]
x.rs:4  let c = &mut a;
                     ^
x.rs:4  let b = &mut a;
                     ^
x.rs:4 }
       ^

Third, tabs seem to be broken on the old error messages? I'm pretty sure they used to work E.g.

src/main.rs:79:35: 79:53 error: failed to resolve. Use of undeclared type or module `mem` [E0433]
src/main.rs:79          Moveable { v: Box::new(unsafe { mem::uninitialized() }) }
                                                 ^~~~~~~~~~~~~~~~~~

[sanxiyn]

span_label is not handled in old format.

[nagisa]

NOTE: I added the code block formatting to the original report.

[sophiajt]

This should be fixed with #33688