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

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

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

Add locking to snc(4) so it is MPSAFE:
- Add a mutex to the softc to protect the softc and device hardware.
- Use a private timer routine to drive the transmit watchdog timer instead
of using if_watchdog/if_timer.
- If if_alloc() fails during attach, fail the attach with an error rather
than panic'ing.
- Clear RUNNING and OACTIVE only in sncstop().
- Don't mess with IFF_UP.
- Don't leak 'struct ifnet' on detach.
- Setup interrupt handler after ether_ifattach().
- Call ether_ifdetach() rather than if_detach() in the pccard detach
routine.

Tested by: no one despite repeated requests

Remove various and sundry NetBSDism's in preparation for adding locking.

Fix -Wundef warnings from compiling GENERIC and LINT kernels of
all architectures.

Stop embedding struct ifnet at the top of driver softcs. Instead the
struct ifnet or the layer 2 common structure it was embedded in have
been replaced with a struct ifnet pointer to be filled by a call to the
new function, if_alloc(). The layer 2 common structure is also allocated
via if_alloc() based on the interface type. It is hung off the new
struct ifnet member, if_l2com.

This change removes the size of these structures from the kernel ABI and
will allow us to better manage them as interfaces come and go.

Other changes of note:
- Struct arpcom is no longer referenced in normal interface code.
Instead the Ethernet address is accessed via the IFP2ENADDR() macro.
To enforce this ac_enaddr has been renamed to _ac_enaddr.
- The second argument to ether_ifattach is now always the mac address
from driver private storage rather than sometimes being ac_enaddr.

Reviewed by: sobomax, sam

Start each of the license/copyright comments with /*-, minor shuffle of lines

Use correct spl mask.

Submitted by: chi@bd.mbn.or.jp (Chiharu Shibata)
MFC after: 1 day

Remove __P.

Added NEC PC-9801-83, 84, PC-9801-103, 104, PC-9801N-25 and PC-9801N-J02R
support which use National Semiconductor DP8393X (SONIC) as ethernet
controller. Currently, this driver is used on only PC-98.

Submitted by: Motomichi Matsuzaki <mzaki@e-mail.ne.jp>
Obtained from: NetBSD/pc98