Fixing ExecutionEngine.run_function OCaml bindings

Hi LLVM hackers,

I would be willing to pay for the open source development

of the ability to execute generated LLVM IR code from OCaml.

I only need support to pass ints as arguments to LLVM IR functions,

and to return ints back to the OCaml worlds.

The feature was added in this commit:

commit 2e855e68d861224c9b61e2bc9cecad1536b1534b

Author: Gordon Henriksen <gordonhenriksen@mac.com>