w1: async netlink, search, fixes, and improvements

This patch series aims to extend and improve the netlink interface to the one wire system. Netlink is exposed as a socket interface which is normally assumed to be asynchronous which only blocks waiting on incoming packets or a fulls end buffer, but were executed on the calling thread. A bus device search can be a lengthy operation and temperature conversion can take 750 ms. With this patch series those lengthy operations are now processed on the thread originally created to do automatic searching, which gives it a reason to exist when automatic search is disabled. Some other improvements for netlink is additional commands to add, remove, and list the known slaves, and send replies only to the requester. They were previously multicast to everyone listening on the group, this required an additional argument to cn_netlink_send.

Search improvements include returning all devices found, as the first that wouldn't fit in a packet would be lost. I marked only this patch for the stable tree, though you would have to have a lot of devices on one bus to hit it. I had a fix to support aborting from netlink rather than just avoiding the oops as the previous patch did. The search can now pick up where it left off, along with setting the maximum number of slaves to search for at a time, a large network could split up the search operation into multiple passes. ds2490 USB dongle now gains support for hardware search and along with not undoing the interface selection operation takes the search for my network from 23.16 seconds to .307346 seconds.

The largest single change is to change the comment style for DocBook to process in addition to comment some additional functions and data structures.