Fixes#260. Reported by František Blahoudek.
The simplification F(f)|q = F(f|q), where q designates an event_univ
formula, was not always applied because of a couple of issue: (1) the
mospliter was ignoring event_univ unless favor_event_univ was set, (2)
when processing formulas from res_EventUniv they were not put back
into res_F or res_G to be subject to the F/G rules.
* spot/tl/simplify.cc: Improve handling of the above points.
* tests/core/reduccmp.test: Adjust and add test case.
* tests/core/ltl2tgba2.test, tests/python/atva16-fig2a.ipynb: Adjust.
