luaPackages.lrexlib: mark as broken

Doesn't build neither with 5.1 nor 5.2 lua.

pkgs/top-level/lua-packages.nix

···
       homepage = "https://github.com/lua-stdlib/lua-stdlib/";
       hydraPlatforms = stdenv.lib.platforms.linux;
       license = stdenv.lib.licenses.mit;
+      broken = true;
     };
   };