This introduces basic support for debugging OCaml binaries.
Use of the native compiler with DWARF emission support (see
https://github.com/ocaml/ocaml/pull/574) is required.
Available variables are considered as 64 bits unsigned integers,
their interpretation will be left to a OCaml-made debugging layer.
Differential revision: https://reviews.llvm.org/D22132
llvm-svn: 277443