- Use a callout instead of the deprecated timeout_handle.
- Set the console name always so that the bvm console device can be used
  via conscontrol even if it isn't chosen as the default console.
o Revamp API between flowtable and netinet, netinet6.
  - ip_output() and ip_output6() simply call flowtable_lookup(),
    passing mbuf and address family. That's the only code under
    #ifdef FLOWTABLE in the protocols code now.
o Revamp statistics gathering and export.
  - Remove hand made pcpu stats, and utilize counter(9).
  - Snapshot of statistics is available via 'netstat -rs'.
  - All sysctls are moved into net.flowtable namespace, since
    spreading them over net.inet isn't correct.
o Properly separate at compile time INET and INET6 parts.
o General cleanup.
  - Remove chain of multiple flowtables. We simply have one for
    IPv4 and one for IPv6.
  - Flowtables are allocated in flowtable.c, symbols are static.
  - With proper argument to SYSINIT() we no longer need flowtable_ready.
  - Hash salt doesn't need to be per-VNET.
  - Removed rudimentary debugging, which use quite useless in dtrace era.

The runtime behavior of flowtable shouldn't be changed by this commit.

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.
Set errno on inet_ntop(3) failure.

Reviewed by:	glebius