* src/commands.c (write_data_line): Factor some code out to ...
(write_data_value): new.
(cmd_listpreorder): New.
* src/preorder.c: Include membuf.h.
(format_columns): New.
(list_preorder_records): New.
(preorder_list_records): New.
* src/payproc-post.c (main): Add command --list-preorder.
(listpreorder): New.