small cleanups

closes https://github.com/official-stockfish/Stockfish/pull/2653

No functional change

src/thread.cpp

@@ -151,7 +151,7 @@ void ThreadPool::set(size_t requested) {
       clear();
 
       // Reallocate the hash with the new threadpool size
-      TT.resize(Options["Hash"]);
+      TT.resize(size_t(Options["Hash"]));
 
       // Init thread number dependent search params.
       Search::init();