Add v208-stable patch series.

This commit was created using the following commands and then fixing up debian/patches/series manually.
$ git config diff.renames false
$ git rebase --onto debian/208-5 v208 stable/v208-stable
$ git checkout -b patch-queue/experimental HEAD
$ gbp-pq export --no-patch-numbers
$ git add --ignore-removal debian/patches/
Update Debian patches to apply on top of v208-stable.
Move three more manpages from systemd to libsystemd-*-dev as appropriate.
Remove pre-generated rules and unit files in debian/rules clean target.

These are generated with rootprefix=/usr and so has the wrong paths for Debian.
Add /run/shm -> /dev/shm symlink in debian/tmpfiles.d/debian.conf
Map SysV runlevel S to basic.target, not sysinit.target.
Merge tag 'upstream/210' into experimental
Add new changelog entry.
Replace v208-stable patch series with v210-stable patch series.
Update Debian patches to apply on top of v210-stable.
Add python-lxml to Build-Depends.
Install the new combined libsystemd0 library
Add new symbols file for libsystemd0.
Install new busctl binary in the systemd package.
Install new translation files in the systemd package.