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 isnanf = __isnanf
! #pragma weak _isnanf = __isnanf
  
  #include "libm.h"
  
  int
  isnanf(float x) {
--- 25,36 ----
  /*
   * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
! #pragma weak __isnanf = isnanf
! #pragma weak _isnanf = isnanf
  
  #include "libm.h"
  
  int
  isnanf(float x) {