Upgrade to mkisofs included in cdrecord-1.8a38.

From AN-1.8a38:

• Fixed a seriuos bug related to the structures iso_path_table and iso_directory_record.
  
  Both structures have an odd length and some compilers (e.g. on Sun3/mc68020 systems) will padd these structures to an even size. For this reason it was a bad idea to use sizeof(iso_path_table) of sizeof(iso_directory_record) for on disk size computations.
  
  The changes affect central functionality and it is needed to do testing if my changes will not introduce a new bug.