MFC r316434:

MFC r316434:
  Add O_EXTERNAL_DATA opcode support.

  This opcode can be used to attach some data to external action opcode.
  And unlike to O_EXTERNAL_INSTANCE opcode, this opcode does not require
  creating of named instance to pass configuration arguments to external
  action handler. The data is coming just next to O_EXTERNAL_ACTION opcode.

  The userlevel part currenly supports formatting for opcode with ipfw_insn
  size, by default it expects u16 numeric value in the arg1.

  Obtained from:	Yandex LLC
  Sponsored by:	Yandex LLC