Line-of-sight output along the z-axis

marked as a Work In Progress

This seems quite inefficient overall with many loops over the particles. We should figure out whether there is a better way of doing things.

Also, it does not compile:

line_of_sight.c: In function 'print_los_info':
line_of_sight.c:102:64: error: format '%lld' expects argument of type 'long long int', but argument 5 has type 'size_t {aka long unsigned int}' [-Werror=format=]
     printf("[LOS %i] Xpos:%g Ypos:%g particles_in_los_total:%lld\n", i,
                                                             ~~~^
                                                             %ld
            Los[i].Xpos, Los[i].Ypos, Los[i].particles_in_los_total);
                                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
line_of_sight.c: In function 'do_line_of_sight':
line_of_sight.c:210:37: error: variable 'LOS_particles_total' set but not used [-Werror=unused-but-set-variable]
     struct line_of_sight_particles *LOS_particles_total;
                                     ^~~~~~~~~~~~~~~~~~~