set_child_below_sibling
Description:
Sets child to be below sibling in the list of children of this.
If sibling is null, child will be the new first child of this.
This function is logically equivalent to removing this and using
insert_child_below, but it will not emit signals or change state
on child.
Parameters:
| this |
a Actor |
| child |
a Actor child of this |
| sibling |
a Actor child of this, or |