File Release Notes and Changelog

Embedded documentation not up-to-date yet. This is how the tarball is supposed to be used:
 * have the OCaml source tarball somewhere, and adapt the Makefile accordingly
 * execute:
     make prepare && cd ocaml-*
     ./configure <your-options>
     make -f Makefile.ocamlduce <target>
   where <target> is one of:
     - world: build only bytecode stuff
     - world.opt: build bytecode and native stuff
     - installbyte: install only bytecode stuff
     - installopt: install only native stuff
     - clean: as usual...
 * enjoy

Initial port to OCaml 3.11.0