Tcl/Tk (X11-based) extension for arm64 macOS 11.

The sources are from
https://sourceforge.net/projects/tktable/files/tktable/2.10/Tktable2.10.tar.gz,
but need to be patched with Tktable.patch for recent Tk (tried with 8.6.11).

To add the binary distribution, download the tarball, preferably using

curl -OL https://www.stats.ox.ac.uk/pub/bdr/Tktable/Tktable.tar.gz

and unpack with

sudo tar -xf Tktable.tar.gz -C /

(and ignore any messages about being unable to change permissions on 
existing directories).