From 0.1 to 0.1a
 - removed a silly bug that prevented the lockfiles for dumping not to
   be erased when the dump was empty. This left a lot of empty lockfiles
   in /tmp. Arghhhh.

From 0.1a to 0.2
 - removed a race condition in the signal handling (SIGCHLD).
   This was introduced when I added the dump process, so it is
   possible for both children to exit at the same time.
   This resulted in a zombie dump process on slow or heavy loaded
   machines.
 - Added pid file creation (/var/run/nacctd.pid a la crond) and
   detection. 

From 0.2 to 0.3
 - made output more configurable. Thanks for inspiration from
   Scott Penrose <scottp@pas.com.au>.

From 0.3 to 0.4
 - added a new way of handling ip - user assignment. Thanks
   for the idea and help in debugging from Bart Kindt <bart@es.co.nz>
 - added a dontignore option
 - cleaned up debugging output
 - made debugging output more configurable
 - default for ignoremask is now really 255.255.255.255 as mentioned in the
   documentation, , i.e. don't ignore anything. You might want to add
   a ignoremask 255.255.255.0 to existing naccttabs, to match the previous
   default
 - fixed a few races in child/signal handling
