Fix a couple of old bugzillas (#737707, #1045922)
    
    - Update mod_vroot to 0.9.3 and drop upstreamed mod_vroot patch
    - Anonymous upload directory specification needs to be slightly different if
      mod_vroot is in use (#1045922)
      http://sourceforge.net/p/proftp/mailman/message/31728570/
    - For systemd-based systems, use systemd rather than xinetd for inetd mode
      activation (#737707); to use this mode, set "ServerType inetd" in
      /etc/proftpd.conf and do "systemctl enable proftpd.socket" (and
      "systemctl start proftpd.socket" to start listening for connections)
    - Use %license where possible