Fix some issues reported by lintian

Fix some issues reported by lintian

• 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)
• Update standards version to 4.6.1, no changes needed. (out-of-date-standards-version)

This merge proposal was created by the Janitor bot, and it will automatically rebase or close this proposal as appropriate when the target branch changes. Any comments you leave here will be read by the Janitor's maintainers.

Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/ocaml-gen/263b8173-38ae-4af5-9e95-6055633521a5.

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/05/fe839a68d98dc6fc2e82cf97737aff7989a550.debug

Files in first set of .debs but not in second

-rw-r--r--  root/root   /usr/lib/debug/.build-id/ac/adfc93c41b3f420fa89ab117c81a4ea37fdd39.debug

No differences were encountered between the control files of package **libgen-ocaml**

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

• Build-Ids: acadfc93c41b3f420fa89ab117c81a4ea37fdd39 05fe839a68d98dc6fc2e82cf97737aff7989a550

No differences were encountered between the control files of package **libgen-ocaml-dev**

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