Precompile file for Distributed

We apparently have a `precompile.jl` file for Distributed.jl (https://github.com/JuliaLang/julia/blob/master/stdlib/Distributed/src/precompile.jl). This was created when Distributed got made into an stdlib and is likely quite a bit out of date right now. It might be worth moving this over to the build time precompile system (or if sufficiently covered, it could just be deleted).