merge with debian-sid, update-po for manpages and fix a few more

Merge ... debian-sid, update-po for manpages and fix a few more
typos in doc/po/es.po to generate the manpages properly.

[ Christian Perrier ]
* German translation update. Closes: #571037
* Spanish manpages translation update. Closes: #573293

[ Julian Andres Klode ]
* cmdline/apt-mark:
  - Use the new python-apt API (and conflict with python-apt << 0.7.93.2).
* apt-inst/contrib/arfile.h:
  - Add public ARArchive::Members() which returns the list of members.
* debian/rules:
  - Fix the libraries name to be e.g. libapt-pkg4.9 instead of
    libapt-pkg-4.9.