Now that the dialogs have some breathing room, split the combo of Tcl/Tk,

Now that the dialogs have some breathing room, split the combo of Tcl/Tk,
IDLE and pydoc into a separate component.  That's almost as big as the
rest of Python (excl. docs and test suite) combined.

Pop up a confimation box if they choose to install at least one of
{Tcl/Tk/IDLE/pydoc, Tools, Test suite} but do not choose to install
Python -- doesn't make much sense, so ask whether that's really what they
want.