The same upstream tarball can be used by multiple uploads so we have to
ignore already existing files.

This reverts commit 58fc1503.

This allows us to remove all obsolete files from the NEW queue even when
the maximum number of removals would be reached normally.

Signed-off-by: NAnsgar Burchardt <ansgar@debian.org>

Include source packages only referenced by Built-Using in per-suite
source indices.

The incoming build queue is now managed by manage-build-queues.

REMOVE :: changesutils.py: no longer in use

Reintroduce the check that all source files for the used format are
actually included.