[R6RS] revised Unicode SRFI

[Michael Sperber]

I really like the revision.

Couple nitpicks:

- There's a vestigial \var{string} in the paragraph under
  `string-normalize-nfkc'.

- Is the restriction of <= 8 hex digits for scalar values really
  necessary, i.e. does it hurt not to give a limit?  This slightly
  gums up specification and implementation.

- "prersentation" -> "presentation"

- I don't much like the name "char-symbol-part?"---the name confused
  me as to its purpose.  How about `char-printable-symbol-part?' ?

- For implementing normalization, CompositionExclusions.txt is also
  needed, I think.  Moreover, it might be worth mentioning that
  CaseFolding.txt contains purely derived information.

- In `string-normalize-nfd', there's a double "normal".  Shouldn't it
  be either `string-nfd' or `string-normalize-d'?

-- 
Cheers =8-} Mike
Friede, Völkerverständigung und überhaupt blabla