Build: silence warning about package wikidoc
Build: silence warning about package wikidoc

Resolves #231.

This is a Unix-specific solution, which may have to be updated in the
future. I am under the impression that even when targeting Win32, the
build environment is still almost always Unix-like, so it may be fine.

rgrinberg/lwt,rgrinberg/lwt,ocsigen/lwt,rgrinberg/lwt,rneswold/lwt,ocsigen/lwt,rgrinberg/lwt,c-cube/lwt,rneswold/lwt,c-cube/lwt,c-cube/lwt,ocsigen/lwt,rneswold/lwt