5261 libm should stop using synonyms.h

*** 25,36 ****
  /*
   * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
! #pragma weak logb = __logb
! #pragma weak _logb = __logb
  
  #include "libm.h"
  #include "xpg6.h"       /* __xpg6 */
  #define _C99SUSv3_logb  _C99SUSv3_logb_subnormal_is_like_ilogb
  
--- 25,36 ----
  /*
   * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
! #pragma weak __logb = logb
! #pragma weak _logb = logb
  
  #include "libm.h"
  #include "xpg6.h"       /* __xpg6 */
  #define _C99SUSv3_logb  _C99SUSv3_logb_subnormal_is_like_ilogb