Fixed code generation of JSON record readers for OCaml 4.02,
as discussed on caml-list
(https://groups.google.com/forum/#!topic/fa.caml/-VnQAC7yRyM
Subject: segfault in simple program with 4.02 native)
Fixed biniou code generator for records under OCaml 4.02, and removed
support for sharing and cycles using 'shared' in ATD syntax. Re-enabling
support for sharing would require new techniques and cannot be done in
pure OCaml (without using Obj).
Version 1.4.0