Reorder by URL

[amallia]

For some weird reason reordering by URL does not work when using https://github.com/pisa-engine/pisa/blob/master/tools/reorder_docids.cpp

It does work if we use this external script instead: https://github.com/pisa-engine/pisa/blob/master/script/generate_sorted_docids_mapping.py

[elshize]

If you remember, can you clarify "does not work"? The only difference between these two I can see is that the python script lowercases the values. Could that be the discrepancy?