Reading the memory statistics requires a call to fopen, which uses the
async-signal-unsafe function malloc. For this reason, interrupting
Madagascar could lead to a crash when coinciding with allocations.
Removing the memory statistics doesn’t do much harm, as this can still
be read from an outside program such as the benchmark runner.
This adds the following statistics: the number of state variables before
and after preprocessing, the number of ground actions before and after
preprocessing, and the maximum size of a strongly connected component.