Adds OCaml libraries: uucd, uunf, uutf and xmlm

Four OCaml libraries contributed by Daniel Bünzli for unicode and xml
processing.

 -  xmlm: Streaming XML codec for OCaml
 -  uutf: Non-blocking streaming Unicode codec for OCaml
 -  uunf: Unicode text normalization for OCaml
 -  uucd: Unicode character database decoder for Ocaml

Homepage: http://erratique.ch/software
Merge pull request #3299 from vbgl/erratique-uu

Adds OCaml libraries: uucd, uunf, uutf and xmlm