title: OpenCV findDataMatrix
body: <p>while i was compiling several opencv-cpp-examples,</p>
  
  <p>i found two errors about DataMatrix</p>
  
  <blockquote>
    <p>error: ‘findDataMatrix’ was not declared in this scope <br>error:
    ‘drawDataMatrixCodes’ was not declared in this scope</p>
  </blockquote>
  
  <p>i looked up objdetect.hpp but i couldn't find out what's wrong.
  i use ubuntu 15.10 &amp; openCV 3.0.0</p>
  
  <p>sample codes are :</p>
  
  <pre><code>Mat frame;
  capture &gt;&gt; frame;
  if (frame.empty())
      break;
  cv::Mat gray;
  cv::cvtColor(frame,gray,CV_RGB2GRAY);
  vector&lt;string&gt; codes;
  Mat corners;
  findDataMatrix(gray, codes, corners);
  drawDataMatrixCodes(frame, codes, corners);
  imshow(window_name, frame);
  </code></pre>