bug#17814: 24.3.91; better string manipulation in subr-x

[Stefan Monnier]

>   (string-match "\\`[\s\t\n\r]*\\(.*?\\)[\s\t\n\r]*\\'" string)
>   (if (or (< 0 (match-beginning 1)) (< (match-end 1) (match-end 0)))
>       (match-string 1 string)
>     string))

The above string-match will fail on a string that has a newline, and the
subsequent code will use whatever was the old match-data, resulting in
broken behavior.

Other than that, I don't have any opinion on such changes (I've never
heard anyone complain about code size or cpu-time of any of those
functions, so I think it largely doesn't matter either way).

        Stefan