Сабж. Текст анонса с changelog'ом: https://controlc.com/1c94bf8a .
Скачать:
https://sourceforge.net/projects/tcl/files/Tcl/8.6.10/tcl8.6.10-src.tar.gz
https://sourceforge.net/projects/tcl/files/Tcl/8.6.10/tk8.6.10-src.tar.gz
https://sourceforge.net/projects/tcl/files/Tcl/8.6.10/tcl8.6.10-html.tar.gz