Fix to old box wrapping error due to rounding

In space_parts_get_cell_index_mapper() and friends, add an additional check that a particle has not been wrapped back onto the exact edge of the box due to rounding differences between the region around 0 and the region around space->dim.

Fixes #665 (closed), #638 (closed), #591 (closed) by using the suggestion of @d74ksy in #591 (closed) and tested by @jch in #665 (closed).

@nnrw56 you may be interested as well.

Any last words from anyone on this?

Looks good to me

mentioned in commit cb6c208a

merged

mentioned in issue #687 (closed)