5910 libnisdb won't build with modern GCC

*** 18,33 ****
   * information: Portions Copyright [yyyy] [name of copyright owner]
   *
   * CDDL HEADER END
   */
  /*
   * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
- #pragma ident   "%Z%%M% %I%     %E% SMI"
- 
  /*
   * DESCRIPTION: Contains the map update thread and related code.
   */
  
  #include <unistd.h>
--- 18,32 ----
   * information: Portions Copyright [yyyy] [name of copyright owner]
   *
   * CDDL HEADER END
   */
  /*
+  * Copyright 2015 Gary Mills
   * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
  /*
   * DESCRIPTION: Contains the map update thread and related code.
   */
  
  #include <unistd.h>
*** 356,365 ****
--- 355,366 ----
  
          /* Free up duplicate copy of the map_ctrl */
          free_map_ctrl(map);
  
          thr_exit(ret);
+ 
+         return (NULL);
  }
  
  /*
   * FUNCTION :   is_special_key()
   *