and a first built-in strgen module. Some tweaks and more default strgens
are needed, but the code doesn't look too bad ;)

... and addes some (later-to-be-removed) debug code to support finding
a problem in transaction handling.

looks like we are almost done and need only to add the ruleset parser-specific
config options.

This is a milestone commit, which adds new code that breaks
nothing, but also does not add any visible change. Just prep work...

I cleaned up a lot of config variable access along the way. This
version compiles and runs, but does not yet offer any enhanced
functionality. pmrfc5424 is just a dummy that is not yet being used.

... but an alternate approach via pthread_kill. This is somewhat safer as we
do not need to think about the cancel-safeness of all libraries we use.
However, not all inputs can easily supported, so this now is a feature
that can be requested by the input module (the most important ones
request it).