* python/spot/aux.py (rm_f): new function.
* python/spot/ltsmin.i: Replace the %require magic by a simple function.
Rewrite the %%dve magic.
* tests/python/otfcrash.py: Simplify using spot.ltsmin.require()
* tests/python/ltsmin.ipynb: Likewise, also add more text for the
documentation.
* NEWS: Adjust.