MFC 253262, 253318, 243184, 253444, 253505, 253520:

- Add a leaf node CTL_NET.PF_ROUTE.0.AF.NET_RT_DUMP.0.FIB.  This returns
  routing table with the specified FIB number, not td->td_proc->p_fibnum.

- Add check_namevarlist() to check if ${name}_var is reserved in
  rc.subr or not.

- Fix a bug in ipv6_prefix_IF.  It did not work with the 64-bit prefix
  notation like 2001:db8:1:1.

- Use eui64 flag in ifconfig(8) instead of network6_getladdr()[*] for
  interface indentifier part.

- Fix address range specification with ifconfig(8) options such as:

  * inet 192.0.2.1-10 netmask 255.255.255.0 (inet range spec + ifconfig options)
  * inet6 2001:db8:1::1-f prefixlen 60 (inet6 range spec + ifconfig options)

  If prefixlen or netmask option is specified with CIDR notation at
  the same time, the option is used.

-  Do not set ND6_IFF_ACCEPT_RTADV on if_bridge(4) interfaces when
   ipv6_enable=yes.

Approved by:	re (marius)