bug#26779: expr length

[Paul Eggert]

A couple of things. First, since performance doesn't matter here, wouldn't it be 
simpler to convert to wide character form by using mbstowcs, do the work in 
wide-character form, and then convert back via wcstombs? The resulting code 
should be easier to maintain, I'd think.

Also, please stick to GNU style for operator spacing and parenthesization.

Thanks.