title: libpng 1.5.10 error: dereferencing pointer to incomplete type
body: <pre><code>png_read_info (png_ptr, info_ptr);
  { 
      png_byte color_type = info_ptr-&gt;color_type;
      png_byte bit_depth  = info_ptr-&gt;bit_depth;
      ...
  </code></pre>
  
  <p>For last 2 lines I get</p>
  
  <blockquote>
    <p>error: dereferencing pointer to incomplete type</p>
  </blockquote>
  
  <p>What's wrong? In libpng 1.4 this was always ok.</p>