modify to make it easy to override 'itemconfiginfo' method.
* ext/tk/lib/tkextlib/tile/treeview.rb : support Tile 0.7.8.
* ext/tk/lib/tkextlib/version.rb : [new] add Tk::Tkextlib_RELEASE_DATE
  to get the information from scripts.
* ext/tk/lib/tk.rb: load 'tkextlib/version.rb', and update RELEASE_DATE.
* ext/tk/lib/tkextlib/SUPPORT_STATUS: update.
* ext/tk/sample/editable_listbox.rb: [new] the listbox with editable
  items. It's one of the example about usage of Place geometry manager.
* ext/tk/sample/tktextio.rb: improve the functions of TkTextIO class.
  Those are required by 'irbtkw.rbw'.
* ext/tk/sample/irbtkw.rbw: [new] IRB on Ruby/Tk. It doesn't need any
  real console. IRB works on a text widget without I/O blocking. That
  is, thread switching on IRB will work properly, even if on Windows.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8@11283 b2dd03c8-39d4-4d8f-98ff-823fe69b080e