Re: string-strip

[Richard Stallman]

    > It isn't useful for the function to provide anything in the match
    > data.  And not saving the match data creates a pitfall that people
    > won't generally expect.  Therefore, it should save the match data.

    Most elisp functions don't bother to save the match data.  That's because it
    is costly to do and rarely useful.

Most functions serve a special purpose and don't have many callers.
This one is a general utility, so we want its interface to be clean.