new functions to define a nested class/module with non-ascii
  name.

* struct.c (make_struct): use name with encoding.

* struct.c (inspect_struct): ditto.  [ruby-core:24849]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@24513 b2dd03c8-39d4-4d8f-98ff-823fe69b080e