Remove global variables from search.h

Globals are not really needed, so redefine as locals.

No functional change.

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

src/uci.cpp

@@ -123,7 +123,7 @@ namespace {
     }
     else if (token == "ucinewgame")
     {
-        TT.clear();
+        push_button("Clear Hash");
         Position::init_piece_square_tables();
         RootPosition.from_fen(StartPosition);
     }