Add test for $dist/updates vs $dist-security

Uses Test::File::Contents, add it to .travis.yml and the according
package as build-dependency in debian/control.

t/data/sources.list.bookworm

@@ -0,0 +1,16 @@
+#
+#  /etc/apt/sources.list
+#
+
+
+#
+# bookworm
+#
+deb     http://deb.debian.org/debian     bookworm main contrib non-free
+deb-src http://deb.debian.org/debian     bookworm main contrib non-free
+
+#
+# Security updates
+#
+deb     http://security.debian.org/ bookworm-security  main contrib non-free
+deb-src http://security.debian.org/ bookworm-security  main contrib non-free

t/data/sources.list.bullseye

@@ -0,0 +1,16 @@
+#
+#  /etc/apt/sources.list
+#
+
+
+#
+# bullseye
+#
+deb     http://deb.debian.org/debian     bullseye main contrib non-free
+deb-src http://deb.debian.org/debian     bullseye main contrib non-free
+
+#
+# Security updates
+#
+deb     http://security.debian.org/ bullseye-security  main contrib non-free
+deb-src http://security.debian.org/ bullseye-security  main contrib non-free

t/data/sources.list.buster

@@ -0,0 +1,16 @@
+#
+#  /etc/apt/sources.list
+#
+
+
+#
+# buster
+#
+deb     http://deb.debian.org/debian     buster main contrib non-free
+deb-src http://deb.debian.org/debian     buster main contrib non-free
+
+#
+# Security updates
+#
+deb     http://security.debian.org/ buster/updates  main contrib non-free
+deb-src http://security.debian.org/ buster/updates  main contrib non-free

t/data/sources.list.sid

@@ -0,0 +1,16 @@
+#
+#  /etc/apt/sources.list
+#
+
+
+#
+# sid
+#
+deb     http://deb.debian.org/debian     sid main contrib non-free
+deb-src http://deb.debian.org/debian     sid main contrib non-free
+
+#
+# Security updates - Uncomment to enable.
+#
+# deb     http://security.debian.org/ sid-security  main contrib non-free
+# deb-src http://security.debian.org/ sid-security  main contrib non-free

t/data/sources.list.stretch

@@ -0,0 +1,16 @@
+#
+#  /etc/apt/sources.list
+#
+
+
+#
+# stretch
+#
+deb     http://deb.debian.org/debian     stretch main contrib non-free
+deb-src http://deb.debian.org/debian     stretch main contrib non-free
+
+#
+# Security updates
+#
+deb     http://security.debian.org/ stretch/updates  main contrib non-free
+deb-src http://security.debian.org/ stretch/updates  main contrib non-free