Disable again buffering at startup

Partially revert efd2167998
Without this patch SF does not send "bestmove" to GUI.

No functional change.

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

src/main.cpp

@@ -17,6 +17,7 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <cstdio>
 #include <iostream>
 #include <string>
 
@@ -35,6 +36,9 @@ extern void kpk_bitbase_init();
 
 int main(int argc, char* argv[]) {
 
+  // Disable output buffering: printf() does not work correctly otherwise
+  setvbuf(stdout, NULL, _IONBF, 0);
+
   bitboards_init();
   Position::init();
   kpk_bitbase_init();