Fix some issues reported by lintian

Fix some issues reported by lintian

• Trim trailing whitespace. (trailing-whitespace)
• Bump debhelper from old 11 to 13. (package-uses-old-debhelper-compat-version)
• Set upstream metadata fields: Archive, Bug-Database, Bug-Submit, Contact, Name, Repository, Repository-Browse. (upstream-metadata-file-is-missing, upstream-metadata-missing-bug-tracking, upstream-metadata-missing-repository)
• Trim trailing whitespace. (trailing-whitespace)
• Bump debhelper from old 12 to 13. (package-uses-old-debhelper-compat-version)
• Set upstream metadata fields: Archive, Bug-Database, Bug-Submit, Contact, Name, Repository-Browse. (upstream-metadata-file-is-missing, upstream-metadata-missing-bug-tracking)

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/gtools/f336fdc8-9e1f-42d0-b0c0-718953c7bd94.

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/8f/79a42f5ffdf08af2549b9de0fd6e53565ee85f.debug

Files in first set of .debs but not in second

-rw-r--r--  root/root   /usr/lib/debug/.build-id/3f/39e9d25dc67f4fd90a55677afaf606b79cc44a.debug

No differences were encountered between the control files of package **r-cran-gtools**

Control files of package r-cran-gtools-dbgsym: lines which differ (wdiff format)

• Build-Ids: 3f39e9d25dc67f4fd90a55677afaf606b79cc44a 8f79a42f5ffdf08af2549b9de0fd6e53565ee85f

You can also view the diffoscope diff (unfiltered).