Add Applied-Upstream header

See merge request !2

Update to upstream version '2.5.3'
with Debian dir 33375072ea3e41ff160ef6f5bb058942778129bb

Changes-By: lintian-brush
Fixes: lintian: upstream-metadata-file-is-missing
See-also: https://lintian.debian.org/tags/upstream-metadata-file-is-missing.html
Fixes: lintian: upstream-metadata-missing-bug-tracking
See-also: https://lintian.debian.org/tags/upstream-metadata-missing-bug-tracking.html

Changes-By: lintian-brush
Fixes: lintian: trailing-whitespace
See-also: https://lintian.debian.org/tags/trailing-whitespace.html

Upstream uses a prefix of 'v.'. 'v' used to be uppercase, and is now
lowercase. Let's accomodate for both, and be ready for the day they drop
the dot.

Gbp-Dch: ignore

Copy/paste from the uscan man page. No understanding required.