app-admin/syslog-ng-2.1.4 Judging from section 9.6 the syslog-ng 2.0 administrator's guide found on BalaBit's website at http://www.balabit.com/dl/guides/syslog-ng-v2.0-guide-admin-en.pdf it seems that the manpage for syslog-ng.conf is out of date. Several of the options listed in the manpage have been deprecated in favor of other options (flush_lines() now for sync()) and others deprecated with no replacement, ineffective since 1.9.x (e.g. gc_busy_threshold() and gc_idle_threshold()). I've not crosschecked the whole manpage, there may be other instances. Reproducible: Always
That's not really a problem with the Gentoo package though so you'll need to take it up with upstream.