Update nodes after a do_move()

And also store the node counter in Position and not in Thread.
This will allow to properly count nodes also in sub trees with
SMP active.

This requires a surprisingly high number of changes
in a lot of places to make it work properly.

No functional change but node count changed for obvious reasons.

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

src/uci.cpp

@@ -57,7 +57,7 @@ namespace {
   // The root position. This is set up when the user (or in practice, the GUI)
   // sends the "position" UCI command. The root position is sent to the think()
   // function when the program receives the "go" command.
-  Position RootPosition(0);
+  Position RootPosition(StartPositionFEN, 0);
 
   // Local functions
   bool handle_command(const string& command);
@@ -82,7 +82,6 @@ namespace {
 
 void uci_main_loop() {
 
-  RootPosition.from_fen(StartPositionFEN);
   string command;
 
   do {
@@ -312,14 +311,13 @@ namespace {
 
     string token;
     int depth, tm, n;
-    Position pos(RootPosition, RootPosition.thread());
 
     if (!(uip >> depth))
         return;
 
     tm = get_system_time();
 
-    n = perft(pos, depth * ONE_PLY);
+    n = perft(RootPosition, depth * ONE_PLY);
 
     tm = get_system_time() - tm;
     std::cout << "\nNodes " << n