snapshotting some benchmarks at first model
added constspace option that discards interpretations once used

(only with --heuristics=monolithic this guarantees correctness!)
killing dlvhex with SIGTERM or with SIGINT (CTRL+C) now also gives benchmark output
the set of benchmarks snapshotted at first model can now be extended in ProgramCtx

(if plugins need to do such a thing)
displaying if we have been killed as error message
aggregates for explicit FLP check
Merge branch 'master' into ps
fixing build if CXX contains spaces
fixing make check with new ModelBuilderConfig