#538 - Analysis with unbounded time

[schillic]

Closes #538.

The second commit is an unrelated bugfix.

[mforets]

What happens if a fixpoint is never found? Instead of an infinite loop, it's better if we have an option to the set maximum number of iterations of the continuous post (by default a "very high" value, and an error message if this value was reached).

Looking into the SpaceEx options (with $ sspaceex --help), I guess that this corresponds to --iter-max,

  --iter-max arg                        Set the maximum number of iterations
                                        for the reachability algorithm.

[schillic]

See #476.