Filter out modules with double underscores

[kit-ty-kate]

Given most libraries nowadays use dune and are packed, every functions will be technically available twice:

• once with the full flatten name
• once with the wrapped module

e.g.

$ dowsindex search "string -> string -> string" | grep "Js_of_ocaml_compiler"
Js_of_ocaml_compiler.Stdlib.String.cat : string -> string -> string
Js_of_ocaml_compiler__Stdlib.String.cat : string -> string -> string
Js_of_ocaml_compiler.Stdlib.Filename.concat : string -> string -> string
Js_of_ocaml_compiler__Stdlib.Filename.concat : string -> string -> string
Js_of_ocaml_compiler.Stdlib.Filename.chop_suffix : string -> string -> string
Js_of_ocaml_compiler__Stdlib.Filename.chop_suffix :

Realistically only the second one is ever used so it would be very handy to detect duplicates and only show the wrapped modules. (an optional argument can be available for users who want the unfiltered output)

[Drup]

__ are currently ordered later, but not hidden. I'm rather squeamish about hiding them completely.

What I would like is rather to have a complete mapping of redefinition/aliases so that we can avoid the problem completely. This requires quite a bit more for the underlying tooling.

[Drup]

Last version uses odoc, which filters things for us !