* need to call SvIV_nomg and SvIV_nomg

  Since perl 5.17.2 Tk's internal magic handling was partially broken.
  When running Tk programs warnings like

      TclObj_get 8027e0c30 int 0'

  could happen.

  This was fixed by changing a SvIV and SvNV call in Tcl_ObjMagic() to
  use their _nomg counterparts.

  With this change the Tk test suite _may- run cleanly again (not
  always, and only under simple window managers like twm)