Allow local modules to self-reference

[janmasrovira]

Consider this example:

module example;

import Library.Delta as Delta;

module Resource;

  module Delta;
  end;

  open Delta; -- ambiguity error between imported Delta and local module Delta.
end;

There exist workarounds to avoid this problem, but most likely the most intuitive is to be able to write open Resource.Delta.

@heueristik recently found this issue when writing the specs in Juvix.