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

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

/* -> /*- for license, minor formatting changes

Get rid of the old *LEN constants in favour of the new *SIZ constants
that also include the trailing \0 byte.

Make the defines that prevent multiple includes look like the
others in netgraph.

Process events from the ATM drivers. Carrier change and PVC change
messages are forwarded as netgraph control messages to the node
that is connected to the manage hook. If that hook is not connected,
the event is lost. Flow control events are converted to netgraph
flow control messages and send along the hook that is connected to
the flow controlled VC. ACR change events are converted to control
messages and sent along the hook for the given VC.

This is a netgraph node to access ATM interfaces. It works with the
hatm(4) and fatm(4) drivers, en(4) will follow soon.