Memcleanup partof memsafety
Integrate property valid-memcleanup into valid-mamsafety, as suggested in the BenchExec implementation [https://github.com/sosy-lab/benchexec/pull/330]
Integrate property valid-memcleanup into valid-mamsafety, as suggested in the BenchExec implementation [https://github.com/sosy-lab/benchexec/pull/330]