Ensure the mixed type of `string|int` is reflected on the `$title` parameter in `wp_die()`.

The ability to pass an error code as short-hand to the `$title` and `$args` parameters was added in r30355. Changes also include cleaned-up formatting and line-wraps for other documentation in the DocBlock.

See [30355]. Fixes #10551.


git-svn-id: https://develop.svn.wordpress.org/trunk@30379 602fd350-edb4-49c9-b593-d223f7449a82