Using `bookmark-jump` would add duplicate overlays when bookmarks were
not at the line beginning
since it checked for an existing overlay at (point), not (point-bol).

This was noticeable when removing the bookmark as the overlay was kept
since removing the overlay only removes one overlay (although it
checks all overlays on the line).

To redo the bug:

- Add a bookmark that isn't at the beginning of the line.
- Jump to this bookmark.
- Delete the bookmark.
- Notice the overlay is not removed.


-- 
- Campbell