Support channel notification decoding status

[chenjunbiao]

使用例子：

	codec, inform := NewStreamingCodec(0x10)
	go func() {
		l := testLoopTimes
		for i := 0; i < l; i++ {
			codec.Decoder(input)
			time.Sleep(100 * time.Millisecond)
		}
	}()

	for {
		select {
		case flag := <-inform:
			if flag {
				v, _ := codec.Read(mold)
				vv := handle(v)
				codec.Write(&verifier{Verify: verify}, vv, mold)
			}
			codec.Refresh(&verifier{Verify: verify})
		case <-time.After(1 * time.Second):
			return
		}
	}