[syslog-ng] create_dir and "dynamic" destinations.

[Fabien Wernli]

Hi Scot,

You have the `create-dirs()` option for that:

http://www.balabit.com/sites/default/files/documents/syslog-ng-ose-3.5-guides/en/syslog-ng-ose-v3.5-guide-admin/html-single/index.html#idp4490112