Reporting speed with -check_media

xorriso/xorriso_private.h

@@ -571,6 +571,7 @@ struct XorrisO { /* the global context of xorriso */
  off_t pacifier_count;
  off_t pacifier_total;
  off_t pacifier_byte_count; /* auxiliary counter for data bytes */
+ off_t pacifier_prev_count; /* internal counter for speed measurement */
 
  void *pacifier_fifo;