version string: add copyright line to version string

Show the copyright when running `ffmpeg -version'. This is useful for
end users trying to determine whether they are using FFmpeg or Libav.
Signed-off-by: Simon Thelen <ffmpeg@c-14.de>

cmdutils.c

@@ -1115,7 +1115,7 @@ void show_banner(int argc, char **argv, const OptionDef *options)
 int show_version(void *optctx, const char *opt, const char *arg)
 {
     av_log_set_callback(log_callback_help);
-    print_program_info (0           , AV_LOG_INFO);
+    print_program_info (SHOW_COPYRIGHT, AV_LOG_INFO);
     print_all_libs_info(SHOW_VERSION, AV_LOG_INFO);
 
     return 0;