5261 libm should stop using synonyms.h

*** 28,38 ****
  
          .file "atan2.s"
  
  #include "libm.h"
  LIBM_ANSI_PRAGMA_WEAK(atan2,function)
- #include "libm_synonyms.h"
  #include "libm_protos.h"
  
          ENTRY(atan2)
          movl    4(%esp),%eax            / low part of y
          movl    12(%esp),%ecx           / low part of x
--- 28,37 ----