provide a hook to report Tcl/Tk version

git-svn-id: https://svn.r-project.org/R/trunk@67174 00db46b3-68df-0310-9c12-caf00c1e9a41
provide a hook to report Tcl/Tk version

git-svn-id: https://svn.r-project.org/R/trunk@67175 00db46b3-68df-0310-9c12-caf00c1e9a41