routine creates a Tcl/Tk interpreter and deletes it. However,
  init cost of Tk's MainWindow is not so small. And that makes it
  impossible to use libraries written with Tcl functions only on
  an environment without a graphical display. This changes support
  delaying initalization of Tk_Stubs until the script needs Tk.
* ext/tk/stubs.h: New file. Define prototypes and return codes of
  functions on stubs.c.
* ext/tk/tcltklib.c: Support delaying initalization of Tk_Stubs
  until the script needs Tk.
* ext/tk/tcltklib.c: Show friendly error messages for errors on
  initialization.
* ext/tk/tcltklib.c: Avoid SEGV on ip_finalize() when ruby is
  exiting and $DEBUG is true. (Not fix. If you know the reason of
  why, please fix it.)
* ext/tk/tkutil/tkutil.c (ary2list, ary2list2): bug fix on handling
  of encoding.
* ext/tk/lib/multi-tk.rb: MultiTkIp#eval_string and bg_eval_string
  don't work propery.
* ext/tk/lib/tk.rb: Forget extending Tk::Encoding module to Tk.
* ext/tk/lib/tk/variable.rb: TkVarAccess fails to initialize the
  object for an element of a Tcl's array variable.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@8860 b2dd03c8-39d4-4d8f-98ff-823fe69b080e