Fix some issues reported by lintian

Fix some issues reported by lintian

• Use secure copyright file specification URI. (insecure-copyright-format-uri)
• debian/copyright: use spaces rather than tabs to start continuation lines. (tab-in-license-text)
• Move source package lintian overrides to debian/source. (old-source-override-location)
• Set upstream metadata fields: Bug-Database, Bug-Submit, Repository, Repository-Browse. (upstream-metadata-file-is-missing, upstream-metadata-missing-bug-tracking, upstream-metadata-missing-repository)

These changes have no impact on the binary debdiff.

You can also view the diffoscope diff (unfiltered).

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Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/php-igbinary/a899d7fb-2482-4128-95ea-0412eea48b45.