Implemented a more reasonable solution for drive truncation with regular files

libisoburn/isoburn.h

@@ -42,8 +42,12 @@ struct isoburn {
  /* Aligned start address to be used for processing (counted in blocks) */
  int nwa;
 
+ /* Truncate to .nwa an eventual regular file serving as output drive */
+ int truncate;
+
  /* Eventual freely fabricated isoburn_disc_get_status().
-    BURN_DISC_UNREADY means that normally emulated status is in effect.
+    BURN_DISC_UNREADY means that this variable is disabled
+    and normally emulated status is in effect.
  */
  enum burn_disc_status fabricated_disc_status;