Add pos negamax function

src/search.h

@@ -0,0 +1,25 @@
+/* search.h - search for perfect move.
+ *
+ * Copyright (C) 2021 Bruno Raoult ("br")
+ * Licensed under the GNU General Public License v3.0 or later.
+ * Some rights reserved. See COPYING.
+ *
+ * You should have received a copy of the GNU General Public License along with this
+ * program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
+ *
+ */
+
+#ifndef SEARCH_H
+#define SEARCH_H
+
+#include <limits.h>
+#include "position.h"
+
+#define EVAL_MIN INT_MIN
+#define EVAL_MAX INT_MAX
+
+eval_t negamax(pos_t *pos, int depth);
+
+#endif  /* SEARCH_H */