Added interlace handling to PNG decoder.

libpng 1.5+ recommends a call to png_set_interlace_handling() if you use
png_read_update_info and png_read_image. It will generate a warning
without it.

modules/highgui/src/grfmt_png.cpp

@@ -277,6 +277,7 @@ bool  PngDecoder::readData( Mat& img )
             else
                 png_set_rgb_to_gray( png_ptr, 1, 0.299, 0.587 ); // RGB->Gray
 
+            png_set_interlace_handling( png_ptr );
             png_read_update_info( png_ptr, info_ptr );
 
             for( y = 0; y < m_height; y++ )