New API calls isoburn_get_attached_start_lba(), isoburn_attach_start_lba()

libisoburn/isoburn.h

@@ -141,6 +141,9 @@ struct isoburn {
  /* Libisofs image context */
  IsoImage *image;
 
+ /* The start LBA of the image */
+ int image_start_lba;
+
  /* The block data source from which the existing image is read.
  */
  IsoDataSource *iso_data_source;