TODO
- C++ support "extern C"
- API versioning
- documentation of Vx and intentions
  v1: one-time global unique identifier
  v3: repeatable not-unique message digest
  v4: one-time local unique identifier
CANDO
- getopt_long support
- a more sophisticated test suite
- more platform support in uuid_mac.c?!
- global locking according to standard?
- persistent/non-volatile state writing?
- additional Perl API for covering Perl language
- additional C API for DCE 1.1 compatibility
- unify pack/unpack/parse/format/dump into:
  typedef enum { UUID_FMT_BIN, UUID_FMT_STR, UUID_FMT_TXT, UUID_FMT_XML } uuid_fmt_t;
  uuid_rc_t uuid_import(uuid_t *_uuid, uuid_fmt_t _fmt, const void  *_buf, size_t _size);
  uuid_rc_t uuid_export(uuid_t *_uuid, uuid_fmt_t _fmt,       void **_buf, size_t _size);