cpow() raises a complex base (a + ib) to a complex exponent (c +
    id).

    cpow(a,b,c,d) is defined as e**((c + id) ln(a + ib)).

                           Entry-Point Names

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

    cpow       S_FLOAT     math$cpow_s    cpowf
               T_FLOAT     math$cpow_t    cpow
               X_FLOAT     math$cpow_x    cpowl
               F_FLOAT     math$cpow_f
               G_FLOAT     math$cpow_g