missing pointer's declaration when enable macro -D_DEBUG_GDB_IO_.

reproducable when "./configure --enable-maintainer-mode CFLAGS=-D_DEBUG_GDB_IO_"

Signed-off-by: Jun Ma <sync.jma@gmail.com>
Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>

src/server/gdb_server.c

@@ -171,6 +171,9 @@ static int gdb_get_char_inner(struct connection *connection, int* next_char)
 	struct gdb_connection *gdb_con = connection->priv;
 	int retval = ERROR_OK;
 
+#ifdef _DEBUG_GDB_IO_
+	char *debug_buffer;
+#endif
 	for (;;)
 	{
 		if (connection->service->type == CONNECTION_PIPE)