libpci: pci_id_lookup - add udev/hwdb support

libpci: pci_id_lookup - add udev/hwdb support

This lets you select hwdb support at compile time.

hwdb is an efficient hardware database shipped with recent versions of udev. It contains
among other sources pci.ids so querying hwdb rather than reading pci.ids directly should give
the same result.

Ideally Linux distros using udev could stop shipping pci.ids, but use hwdb as the only source
of this information, which this patch allows.

Cc: Martin Mares <mj@ucw.cz>