Fix some issues reported by lintian

Fix some issues reported by lintian

• Trim trailing whitespace. (trailing-whitespace)
• Remove 1 obsolete maintscript entry.
• Bump debhelper from old 11 to 13. (package-uses-old-debhelper-compat-version)
• Set debhelper-compat version in Build-Depends. (uses-debhelper-compat-file)
• Fix day-of-week for changelog entry 1.1-1. (debian-changelog-has-wrong-day-of-week)
• Update standards version to 4.6.1, no changes needed. (out-of-date-standards-version)
• Update standards version to 4.6.2, no changes needed. (out-of-date-standards-version)

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 first set of .debs but not in second

-rwxr-xr-x  root/root   DEBIAN/postinst
-rwxr-xr-x  root/root   DEBIAN/postrm
-rwxr-xr-x  root/root   DEBIAN/preinst
-rwxr-xr-x  root/root   DEBIAN/prerm

No differences were encountered in the control files

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/run/a04429db-fc2b-4155-858b-08ef7e3a928a.