Fix some issues reported by lintian

[debian-janitor]

Fix some issues reported by lintian

• Depend on newer debhelper (>= 9.20160709) rather than dh-systemd. (build-depends-on-obsolete-package)
• Use secure URI in Homepage field. (homepage-field-uses-insecure-uri)
• Bump debhelper from deprecated 9 to 12. (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)
• Use secure URI in Vcs control headers: Vcs-Browser, Vcs-Git. (vcs-field-uses-insecure-uri)

This merge proposal was created automatically by the Janitor bot.

You can follow up to this merge proposal as you normally would.

Build and test logs for this branch can be found at
https://janitor.debian.net/lintian-fixes/pkg/prads/e13e361a-66b4-4775-8e42-c78d3877d3f3.

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/e5/7cb5a2dadaab9ea211fff7b5f2802478ea106a.debug
-rw-r--r--  root/root   /usr/share/doc/prads/examples/prads.sql

Files in first set of .debs but not in second

-rw-r--r--  root/root   /usr/lib/debug/.build-id/d0/95760ddffeea50ab2cffe02851956cdf6c77de.debug
-rw-r--r--  root/root   /usr/share/doc/prads/examples/prads.sql.gz

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

• Homepage: [-http​://gamelinux.github.com/prads/-] {+https​://gamelinux.github.com/prads/+}
• Priority: [-extra-] {+optional+}

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

• Build-Ids: [-d095760ddffeea50ab2cffe02851956cdf6c77de-] {+e57cb5a2dadaab9ea211fff7b5f2802478ea106a+}

You can also view the diffoscope diff (unfiltered).