New option: REWRITE_ARGS. This is an improvement over PRIO_LOGIC.
It will rewrite the arguments given on the command-line so that
REPOPRIO is respected. This basically makes PRIO_LOGIC obsolete.
I also changed {r_,}proc_pkgs to not get packages more than
once. Before, an `upgrade alien rlworkman' would have gotten
both atkmm versions.