message: core: enable printf format warnings for cv::format
diff: #include <cstdio>
  +#if defined(__GNUC__) || defined(__clang__) // at least GCC 3.1+, clang 3.5+
  +# define CV_FORMAT_PRINTF(string_idx, first_to_check) __attribute__ ((format (printf, string_idx, first_to_check)))
  +#else
  +# define CV_FORMAT_PRINTF(A, B)
  +#endif
  +
  //! @cond IGNORED
  namespace cv
  @@ -387,7 +393,7 @@ The function acts like sprintf but forms and returns an STL string. It can be us
  message in the Exception constructor.
  @param fmt printf-compatible formatting specifiers.
  */
  -CV_EXPORTS String format( const char* fmt, ... );
  +CV_EXPORTS String format( const char* fmt, ... ) CV_FORMAT_PRINTF(1, 2);
  ///////////////////////////////// Formatted output of cv::Mat /////////////////////////////////
  