Backport ettercap

This one is as simple as Backport par2, except for the strange version: 1:0.7.3-1+b1.

As explained at [1], version +b1 means "1st recompilation", ie the package was recompiled without any change in the source code (but probably with a different build environment).

1: is a version prefix, usually because of a non-incremental version change [2], we don't care about it.

So the source version actually is 1:0.7.3-1, and hence the bpo version will be 1:0.7.3-1~bpo.1.