safra: Use sub-transitions during determinization

* src/tests/safra.cc, src/tests/safra.test:  Update results.
* src/twaalgos/safra.cc, src/twaalgos/safra.hh: The use of transitions
resulted in non deterministic automata.  By using sub-transitions the
problem is solved.

src/tests/safra.cc

@@ -55,6 +55,7 @@ int main(int argc, char* argv[])
         return 2;
       res = tgba_determinisation(aut->aut);
     }
+  res->merge_transitions();
 
   spot::dotty_reachable(std::cout, res);
 }