* ext/tk/lib/tk/image.rb: support to create TkImage object without
  creating a new image object on Tk.
* ext/tk/lib/tk/menu.rb: use TkCommandNames on create_self()
* ext/tk/lib/tk/root.rb: TkRoot.to_eval() returns '.'.
* ext/tk/lib/tk/text.rb: add methods to create a TkText::IndexString
  from (x, y) coords.
* ext/tk/lib/tkextlib/tile.rb: bug fix and update support status.
* ext/tk/lib/tkextlib/tile/*.rb: ditto.
* ext/tk/sample/tkextlib/tile: New demo.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8@8291 b2dd03c8-39d4-4d8f-98ff-823fe69b080e