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 rint = __rint
  
  /*
   * rint(x) return x rounded to integral according to the rounding direction
   * rint(x) returns result with the same sign as x's,  including 0.0.
   */
--- 24,34 ----
  /*
   * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
! #pragma weak __rint = rint
  
  /*
   * rint(x) return x rounded to integral according to the rounding direction
   * rint(x) returns result with the same sign as x's,  including 0.0.
   */