ltlsynt: make sure the previous Xor optimization actually works

* spot/tl/simplify.hh, spot/tl/simplify.cc,
spot/twaalgos/translate.cc: Update the tl_simplification
options after all preferences have been given.
* bin/ltlsynt.cc: Display the size of the translation output.
* tests/core/ltlsynt.test: Add test case.

spot/tl/simplify.cc

@@ -4100,6 +4100,12 @@ namespace spot
     return simplify_recursively(f, cache_);
   }
 
+  tl_simplifier_options&
+  tl_simplifier::options()
+  {
+    return cache_->options;
+  }
+
   formula
   tl_simplifier::negative_normal_form(formula f, bool negated)
   {

spot/tl/simplify.hh

@@ -112,6 +112,14 @@ namespace spot
     /// constructor).
     formula simplify(formula f);
 
+#ifndef SWIG
+    /// The simplifier options.
+    ///
+    /// Those should can still be changed before the first formula is
+    /// simplified.
+    tl_simplifier_options& options();
+#endif
+
     /// Build the negative normal form of formula \a f.
     /// All negations of the formula are pushed in front of the
     /// atomic propositions.  Operators <=>, =>, xor are all removed

spot/twaalgos/translate.cc

@@ -106,10 +106,6 @@ namespace spot
           throw std::runtime_error
             ("tls-impl should take a value between 0 and 3");
         }
-    if (comp_susp_ > 0 || (ltl_split_ && type_ == Generic))
-      options.favor_event_univ = true;
-    if (type_ == Generic && ltl_split_ && (pref_ & Deterministic))
-      options.keep_top_xor = true;
     simpl_owned_ = simpl_ = new tl_simplifier(options, dict);
   }
 
@@ -419,6 +415,18 @@ namespace spot
 
   twa_graph_ptr translator::run(formula* f)
   {
+    if (simpl_owned_)
+      {
+        // Modify the options according to set_pref() and set_type().
+        // We do it for all translation, but really only the first one
+        // matters.
+        auto& opt = simpl_owned_->options();
+        if (comp_susp_ > 0 || (ltl_split_ && type_ == Generic))
+          opt.favor_event_univ = true;
+        if (type_ == Generic && ltl_split_ && (pref_ & Deterministic))
+          opt.keep_top_xor = true;
+      }
+
     // Do we want to relabel Boolean subformulas?
     // If we have a huge formula such as
     //  (a1 & a2 & ... & an) U (b1 | b2 | ... | bm)