TkRev version 9.4.8

A few bugs have been fixed, and the Module Browser now does something when it's in an RCS directory.
But most of the work was on the UI. It looks better on MacOS and has enhancements for Linux/Unix. Way back when I adopted TkCVS and we were all using CDE, I gave it some ability to match the desktop colors. (We had 256 of them!) I've extended it somewhat to sense Gtk3 themes on Gnome-ish and KDE-ish desktops, and also NsCDE. Since I can't test it comprehensively and it may crash, I put it all behind a variable, $cvscfg(match_desktop) which is off by default.