Function gsl_sys::gsl_stats_wvariance_with_fixed_mean

pub unsafe extern "C" fn gsl_stats_wvariance_with_fixed_mean(
    w: *const f64, 
    wstride: usize, 
    data: *const f64, 
    stride: usize, 
    n: usize, 
    mean: f64
) -> f64