rint() rounds x to an integral value according to the current
    IEEE rounding direction specified by the user.

                           Entry-Point Names

    Generic                               Compaq
    Function   Data Type   OpenVMS        Tru64 UNIX
    Name       Required    Alpha          Alpha

    rint       S_FLOAT     math$rint_s    rintf
               T_FLOAT     math$rint_t    rint
               X_FLOAT     math$rint_x    rintl
               F_FLOAT     math$rint_f
               G_FLOAT     math$rint_g