DataStream is a stream that signals end_of_file if the
multipart boundary is encountered. The stream can be reset to
read the next part using multipart_open_next/1. Options:
- close_parent(+Boolean)
 - Close Stream if DataStream is closed.
 
- boundary(+Text)
 - Define the boundary string. Text is an atom, string, code or
character list.
 
All parts of a multipart input can be read using the following
skeleton:
process_multipart(Stream) :-
      multipart_open(Stream, DataStream, [boundary(...)]),
      process_parts(DataStream).
process_parts(DataStream) :-
      process_part(DataStream),
      (   multipart_open_next(DataStream)
      ->  process_parts(DataStream)
      ;   close(DataStream)
      ).
- license
 - - The multipart parser contains code licensed under the
MIT license, based on node-formidable by Felix Geisendoerfer
and Igor Afonov.