Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

MFC 270063: update of netmap code
(vtnet and cxgbe not merged yet because we need some other mfc first)

MFH: sync the netmap code with the one in HEAD
(enhanced VALE switch, netmap pipes, emulated netmap mode).
See details in the log for svn 261909.

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

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

Bring in a number of new features, mostly implemented by Michio Honda:

- the VALE switch now support up to 254 destinations per switch,
unicast or broadcast (multicast goes to all ports).

- we can attach hw interfaces and the host stack to a VALE switch,
which means we will be able to use it more or less as a native bridge
(minor tweaks still necessary).
A 'vale-ctl' program is supplied in tools/tools/netmap
to attach/detach ports the switch, and list current configuration.

- the lookup function in the VALE switch can be reassigned to
something else, similar to the pf hooks. This will enable
attaching the firewall, or other processing functions (e.g. in-kernel
openvswitch) directly on the netmap port.

The internal API used by device drivers does not change.

Userspace applications should be recompiled because we
bump NETMAP_API as we now use some fields in the struct nmreq
that were previously ignored -- otherwise, data structures
are the same.

Manpages will be committed separately.