Issue #15663: Tcl/Tk 8.5.15 is now included with the OS X 10.6+

64-bit/32-bit installer for 10.6+.  It is no longer necessary
to install a third-party version of Tcl/Tk 8.5 to work around the
problems in the Apple-supplied Tcl/Tk 8.5 shipped in OS X 10.6
and later releases.