Add MySQL back to Debian depeendencies

Recent Debian seems to favour MySQL over MariaDb again,
removing the compatibility problem

dist/debian/control

@@ -19,13 +19,13 @@ Description: Multi-protocol RSS/Atom newsfeed synchronization server
  allowing you to use compatible clients for many protocols with a single
  server.
 Depends: ${misc:Depends},
-         dbconfig-sqlite3 | dbconfig-pgsql | dbconfig-no-thanks,
+         dbconfig-sqlite3 | dbconfig-pgsql | dbconfig-mysql | dbconfig-no-thanks,
          php (>= 7.1.0),
          php-cli,
          php-intl,
          php-json,
          php-xml,
-         php-sqlite3 | php-pgsql
+         php-sqlite3 | php-pgsql | php-mysql
 Recommends: nginx | apache2,
             php-fpm,
             php-curl,