Wrong handling of File::Constants in Ruby core docs

There is a wrong representation of File::Constants module as a File::File::Constants: https://docs.ruby-lang.org/en/trunk/File/File/Constants.html.

I believe the root causes are:

• dir.c, defining some constants, parsed before file.c, defining the module;
• special handling of dir.c's definitions here: https://github.com/ruby/rdoc/blob/master/lib/rdoc/parser/c.rb#L455
• ...then I've lost the track :)

I believe that maybe it is a sane solution (as RDoc is Ruby's standard library), to just remove the "hack" and document all the constants in file.c (maybe with help of #ifdef 0, if there is no way to move them completely.

I'm ready for any other suggestions, too (want to fix the inconsistency before Ruby 2.7).

PS: I am not sure if it is related (= if RDoc is used inside), but on ruby-doc.org there are also problems in representation: nesting seems right: https://ruby-doc.org/core-2.6.3/File/Constants.html, but File docs doesn't list the module.

Start with lib/rdoc/parser/c.rb around line 455, then inspect how dir.c and file.c are parsed and how their definitions produce the File::Constants documentation URL. Reproduce the generated documentation and trace why the module is nested as File::File::Constants or omitted from File.html. Done means the generated docs show the module at the correct nesting and list it from File.