5261 libm should stop using synonyms.h

*** 24,34 ****
  /*
   * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
! #pragma weak gamma_r = __gamma_r
  
  #include "libm.h"
  
  double
  gamma_r(double x, int *signgamp) {
--- 24,34 ----
  /*
   * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
! #pragma weak __gamma_r = gamma_r
  
  #include "libm.h"
  
  double
  gamma_r(double x, int *signgamp) {