(boo @buhler )

David Bühler authored 4 years ago and Julien Signoles committed 4 years ago

For a Multiple_map paramater for an option "-option", build by the functor
`Make_multiple_map (Key) (V)`:
when a command line contains a key without a value ("-option key" instead of
"-option key:v"), calls the function [V.of_string key None].