first (explosive) attempt to port openpipe to nqp@parrot

We need this op to actually open a pipe with a given CWD and ENV,
the open("rp") whih parrot provides does not let us pass these.
Merge branch 'master' of github.com:perl6/nqp into openpipe
add working openpipe op for nqp on parrot on linux

That means that we have openpipe on all platforms/backends except
for parrot on windows.
Merge branch 'master' of github.com:perl6/nqp into openpipe
implement openpipe on parrot+windows