* variable.c (rb_mod_constants): when calling Module#constants with
  inherit=false, there is no need to use a hashtable to deduplicate
  constant names. [Feature #9196] [ruby-core:58786]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43956 b2dd03c8-39d4-4d8f-98ff-823fe69b080e