travis-ci: verify Deb packages for PHP 7.1+

The distributions which provides PHP 7.1+ were blocked, because 7.0 (the
PHP version) was hardcoded in package name and installation paths. Now
the problem is resolved and we can verify those packages in CI (and in
the local verification script test.pkg.all.sh).

.travis.yml

@@ -108,7 +108,11 @@ jobs:
     # Debian < 8 (Stretch) do not provide PHP 7.*.
     # Ubuntu < 16.04 (Xenial) do not provide PHP 7.*.
     - env: OS=debian DIST=stretch
+    - env: OS=debian DIST=buster
     - env: OS=ubuntu DIST=xenial
+    - env: OS=ubuntu DIST=bionic
+    - env: OS=ubuntu DIST=disco
+    - env: OS=ubuntu DIST=eoan
 
 python:
   - 2.7

test.pkg.all.sh

@@ -12,7 +12,11 @@ distros="
     fedora:30
     fedora:31
     debian:stretch
+    debian:buster
     ubuntu:xenial
+    ubuntu:bionic
+    ubuntu:disco
+    ubuntu:eoan
 "
 
 if ! type packpack; then