Clearly indicate Ubuntu modified files removed in Debian

Currently, when a file modified in Ubuntu is removed in Debian, MoM marks it C* and keeps the Ubuntu version as .UBUNTU. That's also what happens when such a file is renamed and not removed (as MoM cannot guess that).

Another marker, like R* would be better, with an explanation like this:
"Files marked with 'R*' were modified in Ubuntu and later removed in Debian. Note that a removal may actually hide the fact that the file was renamed to something else, but Merge-o-Matic cannot guess that, so you'll have to find out yourself."