MFC r345797:

MFC r345797:
  Add IPv6 transport for bsnmp.

  This patch adds a new table begemotSnmpdTransInetTable that uses the
  InetAddressType textual convention and can be used to create listening
  ports for IPv4, IPv6, zoned IPv6 and based on DNS names. It also supports
  future extension beyond UDP by adding a protocol identifier to the table
  index. In order to support this gensnmptree had to be modified.

  Submitted by:   harti
  Relnotes:       yes
  Differential Revision:  https://reviews.freebsd.org/D16654