5261 libm should stop using synonyms.h

*** 28,38 ****
  
          .file   "atan.s"
  
  #include "libm.h"
  LIBM_ANSI_PRAGMA_WEAK(atan,function)
- #include "libm_synonyms.h"
  
          ENTRY(atan)
          fldl    4(%esp)                 / push arg
          fld1                            / push 1.0
          fpatan                          / atan(arg/1.0)
--- 28,37 ----