message: sv2017: example p185: add missing module wrap
diff: @@ -8,6 +8,7 @@ virtual function void printB;
  $display("BasePacket::B is %d", B);
  endfunction : printB
  endclass : BasePacket
  +
  class My_Packet extends BasePacket;
  int A = 3;
  int B = 4;
  @@ -18,6 +19,8 @@ virtual function void printB;
  $display("My_Packet::B is %d", B);
  endfunction : printB
  endclass : My_Packet
  +
  +module top;
  BasePacket P1 = new;
  My_Packet P2 = new;
  initial begin
  @@ -29,3 +32,4 @@ P1.printB;
  P2.printA;
  P2.printB;
  end
  +endmodule
  \ No newline at end of file
  