Switch to a const AVCodec *.

This is because newer versions of avcodec return a const AVCodec *.

Signed-off-by: Chris Lalancette <[email protected]>

include/usb_cam/formats/mjpeg.hpp

@@ -233,7 +233,7 @@ class MJPEG2RGB : public pixel_format_base
     std::cerr << m_averror_str << std::endl;
   }
 
-  AVCodec * m_avcodec;
+  const AVCodec * m_avcodec;
   AVCodecContext * m_avcodec_context;
   AVCodecParserContext * m_avparser;
   AVFrame * m_avframe_device;