purge-old-kernels deprecated

[Ralf Mardorf]

PS: Configurations outside of user's home directories are tricky if a
release model distro gets upgraded from one to another release, let
alone rolling releases. Changed files, especially configuration files in
the etc/ directory are usually kept and a newer default config file is
installed by the original name + a suffix. Sometimes it's important to
run a diff command between the used and the new file, to see if changes
require reediting a file. I was used to use the GUI "meld" for this
task, but due to GTK oddities I try to migrate to mcdiff. The Qt
equivalent to "meld", named "kdiff" is a PITA. I want the good old
faithful "meld" back, since mcdiff is quite alright, but not that
comfortable as "meld" when editing.