Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Change s_net to s_node when printing the destination address.

Explicitly specify ATPROTO_DDP constant rather than '0' when binding
a netatalk socket. No functional change.

Add a simple tool to bind netatalk sockets and perform send operations.
This isn't a classic regression test in that it doesn't have a notion of
pass fail, it's more of an exercise tool. It attempts to exercise
unbound, bound, unconnected, and connected variations on SOCK_DGRAM
sockets.