[R6RS] Unicode normalization

[dyb at cs.indiana.edu]

> After experimenting with Unicode normalization and re-reading the SRFI
> discussion, I propose the following simple change to the SRFI:
>
>  * Add `string-normzlize-nfd',
>        `string-normzlize-nfkd',
>        `string-normzlize-nfc', and
>        `string-normzlize-nfkc'.
>    Each of these procedures takes a string and return its D, KD, C, or
>    KC normalization, respectively.

How about (string-normalize 'nfd ---), (string-normalize 'nfkd ---),
etc.  I doubt that the extra dispatch will be costly compared with
the normalization.  This would involve less namespace clutter and
also be a bit more general.

Kent