Returns the value 1 (TRUE) if either or both of the arguments is
    a NaN. Otherwise, it returns the value 0 (FALSE).
    This function is OpenVMS Alpha and Integrity servers only.
    Format
      #include  <math.h>
      double unordered  (double x, double y);
      float unorderedf  (float x, float y);
      long double unorderedl  (long double x, long double y);
1 – Arguments
 x
    A real number.
 y
    A real number.
2 – Return Values
    1                  Either or both of the arguments is a NaN.
    0                  Neither argument is a NaN.