5261 libm should stop using synonyms.h

*** 28,38 ****
  
          .file "atan2f.s"
  
  #include "libm.h"
  LIBM_ANSI_PRAGMA_WEAK(atan2f,function)
- #include "libm_synonyms.h"
  #include "libm_protos.h"
  
          ENTRY(atan2f)
          flds    4(%esp)                 / push y
          flds    8(%esp)                 / push x
--- 28,37 ----