title: tcpdf (html2pdf) is not generating table borders correctly
body: <p>I am generating pdf file using html2pdf (that is using tcpdf library, _tcpdf_5.0.002). Unfourtunately I cannot generate table borders properly.</p>
  
  <pre><code>require_once('inc/html2pdf/html2pdf.class.php');
  $html2pdf = new HTML2PDF('P','A4','en');
  $pdf_output = '';
  
  // HEADER
  $pdf_output .='&lt;page backtop="8mm" backbottom="8mm" backleft="10mm" backright="10mm" style="font-size: 11px;font-family:freeserif;"&gt;';
  $pdf_output .= '&lt;style&gt; 
      table {
          border-collapse:collapse;
      }
      &lt;/style&gt;';
  
   $pdf_output.='&lt;table&gt;';
   $pdf_output.= '&lt;tr&gt;&lt;td style="border-top: 1px solid black;"&gt;A&lt;/td&gt;&lt;/tr&gt;';
   $pdf_output.= '&lt;tr&gt;&lt;td style="border-top: 1px solid black;"&gt;A&lt;/td&gt;&lt;/tr&gt;';
   $pdf_output.= '&lt;tr&gt;&lt;td style=""&gt;A&lt;/td&gt;&lt;/tr&gt;';
   $pdf_output.= '&lt;tr&gt;&lt;td style="border-top: 1px solid black;"&gt;A&lt;/td&gt;&lt;/tr&gt;';
   $pdf_output.='&lt;/table&gt;';
   $pdf_output .='&lt;/page&gt;';
   $html2pdf-&gt;WriteHTML($pdf_output);
   $attachment= $html2pdf-&gt;Output('attachment.pdf', 'S');
   ...
  </code></pre>
  
  <p>It doesn't show top borders for cells. It shows top-border only for first row and not for others. I have simplified this html markup for test purposes (in reality it doesn't render just "A" letters in one cell, there is content in differnt columns, but top-border is not rendering either).</p>
  
  <p>How to render top-border for cells ucing html2pdf (tcpdf)? </p>