Support string conversion to unpacked array

[wsnyder]

sv-tests 5.9-string-word-assignment.sv checks IEEE 5.9 conversion from string to packed arrays. Only Aldec seems to correctly support this, but would be good to get a green box for this. Should only need V3Width::iterateCheck improvements.

module t();
   bit [8 * 3 - 1 : 0] a = "hi0";
   // Note as of January 2020 several commercial simulators do not support unpacked byte
   // assignment from strings:
   byte                bb[3 : 0];
   byte                bl[0 : 3];
   initial begin
      bb = "hi2";
      bl = "lo3";
      $display("bb=%p [0]=%x", bb, bb[0]);
      $display("bl=%p [0]=%x", bl, bl[0]);
      if (bb[3] != "h") $stop;
      if (bb[2] != "i") $stop;
      if (bb[1] != "2") $stop;
      if (bb[0] != 0) $stop;
      if (bl[0] != "l") $stop;
      if (bl[1] != "o") $stop;
      if (bl[2] != "3") $stop;
      if (bl[3] != 0) $stop;
   end
endmodule

[wsnyder]

Added in 5.002 4f4c263