Added small configure script (temporary solution)
By default, it will look for MPI sources in /usr/includes/openmpi-x86_64, and
installs generated files in the .opam directory in lib/ocamlmpi. However its a
temporary solution, and it doesn't generate META files required by opam and
ocamlfind. To specify another directory for includes AND destination :
./configure <MPI include dir> <destination dir>

(PS : Yes, its written in OCaml since I suck with sh scripts)