ZLARGV generates a vector of complex plane rotations with real
 cosines, determined by elements of the complex vectors x and y.
 For i = 1,2,...,n

    (        c(i)   s(i) ) ( x(i) ) = ( r(i) )
    ( -conjg(s(i))  c(i) ) ( y(i) ) = (   0  )

    where c(i)**2 + ABS(s(i))**2 = 1

 The following conventions are used (these are the same as in ZLARTG,
 but differ from the BLAS1 routine ZROTG):
    If y(i)=0, then c(i)=1 and s(i)=0.
    If x(i)=0, then c(i)=0 and s(i) is chosen so that r(i) is real.

          N is INTEGER
          The number of plane rotations to be generated.

          X is COMPLEX*16 array, dimension (1+(N-1)*INCX)
          On entry, the vector x.
          On exit, x(i) is overwritten by r(i), for i = 1,...,n.

          INCX is INTEGER
          The increment between elements of X. INCX > 0.

          Y is COMPLEX*16 array, dimension (1+(N-1)*INCY)
          On entry, the vector y.
          On exit, the sines of the plane rotations.

          INCY is INTEGER
          The increment between elements of Y. INCY > 0.

          C is DOUBLE PRECISION array, dimension (1+(N-1)*INCC)
          The cosines of the plane rotations.

          INCC is INTEGER
          The increment between elements of C. INCC > 0.

  6-6-96 - Modified with a new algorithm by W. Kahan and J. Demmel

  This version has a few statements commented out for thread safety
  (machine parameters are computed on each entry). 10 feb 03, SJH.