refactor: use C++11 default initializers

src/bench/checkqueue.cpp

@@ -30,8 +30,7 @@ static void CCheckQueueSpeedPrevectorJob(benchmark::Bench& bench)
 
     struct PrevectorJob {
         prevector<PREVECTOR_SIZE, uint8_t> p;
-        PrevectorJob(){
-        }
+        PrevectorJob() = default;
         explicit PrevectorJob(FastRandomContext& insecure_rand){
             p.resize(insecure_rand.randrange(PREVECTOR_SIZE*2));
         }