syslog-ng 3.5.5 compatibility

syslog-ng 3.5.5 introduced an incompatible change in value-pairs, in
order to allow time-zone settings to propagate to value-pairs. This
patch ups the syslog-ng dependency, and updates all relevant modules.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Merge pull request #73 from algernon/f/syslog-ng-3.5.5

syslog-ng 3.5.5 compatibility