a6df3 is the initial commit of branch seahorn

- allow multiple -I dir, will be used in order (first one declared
  is first used)

- when declaring a global library #open <foo>, foo is first checked
  in local folders, than in global one (install path). This
  does not apply to local libraries opened with #open "foo".

- Version now includes current git branch

- no more classic display for ocamlc
- compilation warnings removed

Non regression results were similar to master branch

functional: keep it as is
non func: introduce a fresh local var v and replace assert(e) by v=e; assert (v);

mostly a recovery of an ancient svn repo: mutations

nice bug correction wrt constants with a large number of digits. Would raise exception when comparing these constants