daptup: libcupt1 backend: removed as obsolete
daptup: is a pure plugin now, specifying subcommand is now mandatory
manpage: see also: removed obsolete reference to 'apt-show-versions', added reference to 'cupt'
manpage: author: updated my mail address
manpage: options: '--post' always collect new changes
daptup: got rid of '[done]' message parts
daptup: find_old_packages: don't attempt to write to an non-opened file descriptor