Fix some issues reported by lintian

Fix some issues reported by lintian

• Trim trailing whitespace. (trailing-whitespace)

• Use secure copyright file specification URI. (insecure-copyright-format-uri)

• Update watch file format version to 4. (older-debian-watch-file-standard)

• Bump debhelper from deprecated 9 to 13. (package-uses-deprecated-debhelper-compat-version)

• Set debhelper-compat version in Build-Depends. (uses-debhelper-compat-file)

• Change priority extra to priority optional. (priority-extra-is-replaced-by-priority-optional)

• Update Vcs-* headers from URL redirect. (vcs-obsolete-in-debian-infrastructure)

• Use canonical URL in Vcs-Git. (vcs-field-not-canonical)

This merge proposal was created automatically by the Janitor bot. For more information, including instructions on how to disable these merge proposals, see https://janitor.debian.net/lintian-fixes.

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The bot will automatically update the merge proposal to resolve merge conflicts or close the merge proposal when all changes are applied through other means (e.g. cherry-picks). Updates may take several hours to propagate.

Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/clog/f1e9b9de-52c2-4fda-ad4f-e599233f05b0.

Debdiff

These changes affect the binary packages:

[The following lists of changes regard files as different if they have different names, permissions or owners.]

Files in second set of .debs but not in first

-rw-r--r--  root/root   /usr/lib/debug/.build-id/21/bc683b4d271f3c53e29f9d7729dbd7e927dc52.debug

Files in first set of .debs but not in second

-rw-r--r--  root/root   /usr/lib/debug/.build-id/e5/cfaef4043c0cdd7650cc41a2dd8098e3bcffcc.debug

Control files of package clog: lines which differ (wdiff format)

• Priority: extra optional

Control files of package clog-dbgsym: lines which differ (wdiff format)

• Build-Ids: e5cfaef4043c0cdd7650cc41a2dd8098e3bcffcc 21bc683b4d271f3c53e29f9d7729dbd7e927dc52

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