build issues / ocaml-libs

[rauhbein]

In INSTALL.md it says ocaml 4.00.0 works with Lem but it apparently doesn't, after checking README.md I found out only 4.02.0 is supported and I was able to build lem.

Also the ocaml-libs build needs ocamlfind which does not seem to come with either versions.

The ocaml backend itself seems to have some dependencies itself e.g. zarith, but make install_dependencies seems to copy shared objects to a 4.05.0 subfolder in /usr/local/lib/ocaml where make ocaml-libs does not find dllzarith.so. Had to copy it manually to /usr/local/lib/ocaml/stublibs make it build.