- add "--pci 00:1f.3" option to easily specify a PCI device instead of having to
  use --bus, --dev, and --func.

- memset + snprintf looks dubious

- pci_get_ndevs should be deprecated, applications shouldn't be relying on this

- we shouldn't duplicate pci_access.[ch] x86_pci.[ch] from libpciaccess, we
  should get libpciaccess to expose pci_system_x86_create() to keep the
  maintenance of x86 port knocking there.

  At least one difference with libpciaccess is the refresh operation. Perhaps
  we'd need to extend libpciaccess to fix that.

  BTW we could also support libpci.
