EASY
~~~~
* Constantly improving configure.ac by autoscan (from autoconf), as
  we add new C code here and there.
* Drop libjte_private.h, merge with jte.h which is equally private
* Drop 'extern' from function declaration in *.h.
* Rename endian.c to endianconv.h to match the private header?

NOT SO EASY
~~~~~~~~~~~
* Write a cousin to list_file_in_jigdo() without calculating md5 inside,
  since it is likely image-generators already have that computed.

  A side effect to avoid: a matched file will get read three times so far:
  - In list_file_in_jigdo() by calculate_md5sum(filename, size, md5);
  - In write_jt_match_record() by if ((infile = fopen(filename, "rb")) == NULL) {
  - By the IsoFileSource object in the libisofs data file loop.
  Should that be optimized a bit? How?

* Jigdo production does not play well with ISO 9660 multi-session.
  Multi-session on disk files implies overwriting of the Volume Descriptors
  at block 16 ff. To overwrite the corresponding piece in a template file
  seems to be quite a challenge. Compressed size might change.
  So for now: single session images only.
  
