11175 libm should use signbit() correctly
11188 c99 math macros should return strictly backward compatible values

*** 64,80 ****
   * C99 7.12.3 classification macros
   */
  #undef  isnan
  #undef  isinf
  #if __GNUC__ >= 4
- #define isnan(x)        __builtin_isnan(x)
- #define isinf(x)        __builtin_isinf(x)
  #define fpclassify(x)   __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL, \
      FP_SUBNORMAL, FP_ZERO, x)
! #define isfinite(x)     __builtin_isfinite(x)
! #define isnormal(x)     __builtin_isnormal(x)
! #define signbit(x)      (__builtin_signbit(x) > 0)
  #else  /* __GNUC__ >= 4 */
  #define isnan(x)        __extension__( \
                          { __typeof(x) __x_n = (x); \
                          __builtin_isunordered(__x_n, __x_n); })
  #define isinf(x)        __extension__( \
--- 64,80 ----
   * C99 7.12.3 classification macros
   */
  #undef  isnan
  #undef  isinf
  #if __GNUC__ >= 4
  #define fpclassify(x)   __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL, \
      FP_SUBNORMAL, FP_ZERO, x)
! #define isnan(x)        __builtin_isnan(x)
! #define isinf(x)        __builtin_isinf(x)
! #define isfinite(x)     (__builtin_isfinite(x) != 0)
! #define isnormal(x)     (__builtin_isnormal(x) != 0)
! #define signbit(x)      (__builtin_signbit(x) != 0)
  #else  /* __GNUC__ >= 4 */
  #define isnan(x)        __extension__( \
                          { __typeof(x) __x_n = (x); \
                          __builtin_isunordered(__x_n, __x_n); })
  #define isinf(x)        __extension__( \