5261 libm should stop using synonyms.h

*** 24,34 ****
  /*
   * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
! #pragma weak atan2 = __atan2
  
  #include "libm.h"
  
  /*
   * Let t(0) = 1 and for i = 1, ..., 160, let t(i) be the slope of
--- 24,34 ----
  /*
   * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
! #pragma weak __atan2 = atan2
  
  #include "libm.h"
  
  /*
   * Let t(0) = 1 and for i = 1, ..., 160, let t(i) be the slope of