Teach 'bench' to run current position

Now that we can call bench from command prompt
has a sense to teach bench to run the current
set position. To do this is enough to call bench
with 'current' as fen source parameter.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/uci.cpp

@@ -59,6 +59,8 @@ void uci_loop(const string& args) {
   Position pos(StartFEN, false, Threads.main_thread()); // The root position
   string cmd, token;
 
+  Search::RootPosition = pos;
+
   while (token != "quit")
   {
       if (!args.empty())