This update for mailman fixes the following issues:

- updated mailman-apache2.conf to support "require" syntax of recent apache httpd (boo#975618)
- update to 2.1.21
* new dmarc_none_moderation_action list setting
* new feature to automatically turn on moderation for single list members (spam prevention)
* new mm_cfg.py setting GLOBAL_BAN_LIST
* translation updates and bug fixes
* for more details see NEWS and Mailman/Defaults.py