bug#25599: Why edit markers after insert?

[nitish chandra]

Only marker originally pointing inside the deleted region were recorded
here, and this is to make sure they regain their previous position after
the reinsertion.

I removed this part of the code to see what changes.

1. I put a marker in a line

2. Deleted the line

3. Undo-ed the delete

The marker is still in the proper place. So markers in the deleted string do seem to regain their position properly.