Returns the complex square root of its argument.
    This function is OpenVMS Alpha and Integrity servers only.
    Format
      #include  <complex.h>
      double complex csqrt  (double complex z);
      float complex csqrtf  (float complex z);
      long double complex csqrtl  (long double complex z);
1 – Argument
 z
    A complex value.
2 – Description
    The csqrt functions compute the complex square root of z, with a
    branch cut along the negative real axis.
3 – Return Values
    x                  The complex square root value in the range of
                       the right half-plane (including the imaginary
                       axis).