[PATCH x4] hurd: pci-arbiter and rumpdisk static server support

[Damien Zammit]

Hi all,

This has been a work in progress for some time.
I am hoping it does not need much reworking.

The only problem I can see is the uid=0 faking the cred by allowing
netfs to install ports that have no cred at all, perhaps we need
a new RPC for obtaining a temporary uid=0 cred during bootstrap?
(I don't know how to make it appear in the protid, for example).

With these changes, plus the pciaccess change I will post shortly,
rumpdisk.static boots with pci-arbiter.static as the bootstrap server.

I have reported a bug upstream with qemu because running Hurd as a guest
crashes qemu randomly with a strange message from the rumpdisk AHCI driver:

https://bugs.launchpad.net/qemu/+bug/1917442

Thanks,
Damien Z