Merge: neo_doxygen: Support namespaces’ members

In some languages, like Python, the immediate parent of a member is not necessary a class. So, for cases when namespace as direct members, add an implicit class named `(self)` to list them in a Nit model.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>

Pull-Request: #985
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>

diff --cc tests/nitg-g.skip
index 973baf6,e901186..d25129d
--- 1/tests/nitg-g.skip
--- 2/tests/nitg-g.skip
+++ b/tests/nitg-g.skip
@@@ -5,7 -5,8 +5,8 @@@ neo_doxygen_dum
  neo_doxygen_file_compound
  neo_doxygen_graph_empty_project
  neo_doxygen_member_resolve_introducer
+ neo_doxygen_namespace_members
  test_docdown
  nith
 -nit_pretty
 +nitpretty
  nitmetrics