patch for bug 487 by Dominic Jänichen

git-svn-id: https://foundry.supelec.fr/svn/luatex/trunk@4988 0b2b3880-5936-4365-a048-eb17d2e5a6bf
update mplib to connect with the Lua interpreter

git-svn-id: https://foundry.supelec.fr/svn/luatex/trunk@4998 0b2b3880-5936-4365-a048-eb17d2e5a6bf