Changes: attribution information for 4.01
    
    I had collected attribution information for the announce only, but
    Damien agreed to put them in the Changes file as well.
    
    This change also fixes minor problems with the Changes content:
    - type-based disambiguation of constructors and labels was not mentioned
    - the open! syntax was not mentioned
    - PR#5552 was mislabeled
    - PR#5758 (matching on floats) was announced despite being also
      present in the 4.00.1 changes
    - I moved PR#5986 (Marshal.Compat_32) from 'bug' to 'feature'
    - PR#5243 was absent (ocamlbuild API documentation)
    
    git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.01@14088 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02