New API function iso_write_opts_set_part_offset() controls creation of

an MBR with a first partiton table entry that bears non-zero start address.
A second set of volume descriptors and directory tree+tables gets created
which can be used to mount the image at the partition start.
Not yet implemented for second set: ISO 9660:1999, MD5 checksums.

libisofs/joliet.h

@@ -54,4 +54,10 @@ struct joliet_node
  */
 int joliet_writer_create(Ecma119Image *target);
 
+
+/* TWINTREE: Not to be called but only for comparison with target->writers[i]
+*/
+int joliet_writer_write_vol_desc(IsoImageWriter *writer);
+
+
 #endif /* LIBISO_JOLIET_H */