Calls using METH_OLDARGS unpack this tuple; calls using METH_VARARG
don't.  Tcl's concatenation of args was affected; IDLE doesn't start.

Modify Tkapp_Call() to unpack single tuple arglists.

Bug 1733943
Ref http://mail.python.org/pipermail/python-checkins/2007-May/060454.html