PCI Arbiter

[Joan Lledó]

Hello Hurd,

This is a new version of the PCI arbiter. Following are some features I've
added the project over the last weeks.

- A tiny libnetfs filesystem to expose a tree of devices.
- For each virtual device, provide files to read/write its configuration space,
  regions an expansion rom.
- Ability to set access permissions over devices by command line parameter and
  fsysopts.

I tried to run netdde as non-root but gave up because it seemed non-trivial for
me and the time for my thesis is running out. Next are some issues I found:

- Some network drivers poke IO ports by themselves (See #hurd, 2017-11-23 [1]).
- check_kernel() in check_kernel.c[2] is calling get_privileged_ports().

Besides, the pci server lacks some features required to run netdde as non-root:

- Provide some way for the client to map device's regions and rom into its
  space. read() + mmap() could be enough for read-only spaces, but probably
  making the server act as a pager is the only good solution.
  (See #hurd, 2017-10-27 [3]).
- Provide libpciaccess and pciutils with a way to poke IO ports as non-root.
  Adding new routines to the PCI interface is an option, or even creating a
  new interface, since poking IO ports is not necessarily related to PCI.

Modules for libpciaccess and pciutils are also attached.

------------------------
[1] http://richtlijn.be/~larstiq/hurd/hurd-2017-11-23
[2] https://anonscm.debian.org/cgit/pkg-hurd/netdde.git/tree/check_kernel.c
[3] http://richtlijn.be/~larstiq/hurd/hurd-2017-10-27