Function sulis_state::calculate_los

#[must_use]pub fn calculate_los(
    exp: &mut Vec<bool>, 
    area: &GeneratedArea, 
    prop_vis_grid: &[bool], 
    prop_grid: &[Vec<usize>], 
    entity: &mut EntityState, 
    delta_x: i32, 
    delta_y: i32
) -> HashSet<usize>