Support timelimit on Windows

[Halbaroth]

We do not support timelimit and :reproducible-resource-limit on Windows because our implementation relies on Unix signals. We should support them using GC alarms as it does in Dolmen.

[bclement-ocp]

Note: we should use step bounds for reproducible-resource-limit (but we don't support per-goal step bounds at the moment). As per the SMT-LIB specification it must be guaranteed that running the same code on the same machine with the same reproducible-resource-limit give the same result, so using real time does not actually implement the specification (it is not reproducible).