Automate build for 0compile
Added Dynlink.lookup_module
Make Dll use the correct suffix for the current platform, not the build platform

Otherwise, programs compiled on Linux using Dynlink will still try to
open '.so' files on Windows, rather than '.dll' files.
ocaml toplevel: add script's directory to the search path

Before, we added the current directory instead, which is less useful and
a security risk (e.g. consider running a program while in /tmp).