ZROT   applies a plane rotation, where the cos (C) is real and the
 sin (S) is complex, and the vectors CX and CY are complex.

          N is INTEGER
          The number of elements in the vectors CX and CY.

          CX is COMPLEX*16 array, dimension (N)
          On input, the vector X.
          On output, CX is overwritten with C*X + S*Y.

          INCX is INTEGER
          The increment between successive values of CY.  INCX <> 0.

          CY is COMPLEX*16 array, dimension (N)
          On input, the vector Y.
          On output, CY is overwritten with -CONJG(S)*X + C*Y.

          INCY is INTEGER
          The increment between successive values of CY.  INCX <> 0.

          C is DOUBLE PRECISION

          S is COMPLEX*16
          C and S define a rotation
             [  C          S  ]
             [ -conjg(S)   C  ]
          where C*C + S*CONJG(S) = 1.0.