renumber: replace in <obj>, that must be of integer type, the values of the list <old_ids> by the values of <new_ids>
<old_ids> and <new_ids> must be intarray, and if <new_ids> is missing it is assumed as an increasing array starting from 0
objarray renumber <obj> <old_ids> ?<new_ids>?
e.g.
set obj [objarray new intarray -values {10 15 3 15 20 3}]
-> 10 15 3 15 20 3
set old_ids [objarray new intarray -values {3 10 15 20}]
objarray renumber $obj $old_ids
-> 1 2 0 2 3 0