message: sv2017: example p573: add missing module wrap
diff: +module top;
  + bit [7:0] v_a, v_b;
  covergroup cg @(posedge clk);
  a: coverpoint v_a
  {
  @@ -13,10 +15,11 @@ bins b2 = { [1:84] };
  bins b3 = { [85:169] };
  bins b4 = { [170:255] };
  }
  -c : cross a,
  + c : cross a, b
  {
  bins c1 = ! binsof(a) intersect {[100:200]};// 4 cross products
  bins c2 = binsof(a.a2) || binsof(b.b2);// 7 cross products
  bins c3 = binsof(a.a1) && binsof(b.b4);// 1 cross product
  }
  endgroup
  +endmodule
  \ No newline at end of file
  