chg: upgrade client to use "setumask2" command No compatibility code is added to the client side, since it's unlikely for new client to communicate with the old server.

chgserver: add "setumask2" command which uses correct message frame The first 4 bytes should be a length field, not a value. Spotted while porting chg functions to the Rust one.

packaging: "make deb" no longer fails Release 4.7 rationalized the layout of the build scripts. Unfortunately, while "make docker-ubuntu-*" and "make docker-debian-*" worked as expected, "make deb" was broken. Before this change "make deb" was failing with the following error: You are not inside a Mercurial repository! Or, after the latest changes: You are inside <fullpath>, which is not the root of a Mercurial repository Moreover, when "make deb" failed, the cleanup routine deleted the wrong directory (contrib/packaging/debian instead of <reporoot>/debian) resulting in a corrupted working copy that needed to be hg revert-ed. After this change the docker targets continue to work, and the deb one is able to finish.