core_actions.c: Avoid re-adding already existing target values in the setvar action.
ironbeepp/hooks.cpp: Fix invalid assumption on hook parameters.
engine/tests/tc_core_actions: Clean up on new test:

1. No longer needlessly loads Lua module.
2. No longer needlessly loads Predicate module.
3. Removed dead code.
4. Removed unnecessary {}
5. Removed non-existent "message" directive.
engine/tests/tc_core_actions: More cleanup:

1. Removed unneeded directives.
2. Removed unneeded headers.
3. Removed unneeded response.
ironbeepp/transaction.cpp: Fix bug in request_header() and response_header() which no headers available. RNS-844
modhtp: Warn, not assert if parameter values are invalid.