German dpkg translation update

Update to 1087t, thanks to Helge Kreutzmann for his suggestions.
debian: Correct Zhou Mo name
po: Update Simplified Chinese program translations

Signed-off-by: Guillem Jover <guillem@debian.org>
po: Update Vietnamese programs translation

Signed-off-by: Trần Ngọc Quân <vnwildman@gmail.com>
Signed-off-by: Guillem Jover <guillem@debian.org>
dpkg: Add a requeueing insertion protection for process_queue()

We should not requeue packages already in the queue. Just protect it
in a similar way in how the deferred triggers queue is protected. In
the future these can be unified.
dpkg: Add a debug line for each package processed in the queue

This gives a general overview of the current progress.
dpkg: Make sure to always switch to the next dependtry after no progress

We might get into a situation where we are making no progress, and
dependencies_ok() is still telling us that we can make progress by
fixing some triggers awaited package, but if those packages require
a dependency cycle to be broken we will get stuck and not progress to
the next dependtry.

Add an additional hard limit where we will jump dependtry, in case we
are not making any progress. This is a safety net that was removed when
triggers got introduced, but that only became active when adding the
dependency checks to trigproc(), although it was never future-proof.

Regression introduced in commit 10440009b68f59eeed4cb1b56547e3cf356aa540
and commit e121d882c92099d1f1aa9eedd0c0e90806a44efa.

Closes: #766242, #766322
dpkg: Make the initial dependtry be 1 instead of 0

This gets rid of an unused dependtry step, which got accidentally
introduced when the perl dpkg was rewritten in C, ages ago.
Dpkg::Source::Package::V2: Allow detached upstream signatures

Upstream tarballs usually come with detached signatures, which would be
useful to have in the source package, as an additional check that could
be performed to verify its integrity and provenance.

For now just allow the detached signatures to be listed in the file
fields in the source control file (.dsc).

Closes: #759478
Suggested-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
po: Unfuzzy strings
u-a: Inline alternative status description into translatable string

This makes it possible to correctly translate the string.

Required-by: #766311
dpkg(1): Reword description for installed status

Prompted-by: #752123
Regenerate .pot files and merge .po files with them
Release 1.17.20
Bump version to 1.17.21