actual idiag code

Hi -

Here is a more legit attempt at supporting the inetdiag netlink family. Let me know what you'd like me to change to get this into an acceptable state.

The big thing are the enums I created in idiagnl.h which replicate parts of linux/inet_diag.h -- I wasn't sure what would be the best way to handle this since different users will surely have different kernel headers installed. I posted about this to the mailing list, but figured I may as well submit a pull request since I'm sure there will be other things you'd like me to adjust/change.

Thanks for your time,
Joe