1) Add a comment to the help file to that points to the
   preferences menu.

2) An earlier checkin tried to detect Tk >= 8.10.14,
   but did this in the wrong way. The end result of this
   was that the IDLE->Preferences... menu got surpressed
   when using the system version of Tcl/Tk

_PyObject_GC_TRACK is the macro version of PyObject_GC_Track,
and according to documentation it should not be used for extension modules.

file with `str' filename on Windows.

in struct's L format.

put them into dis.__all__.