[ticket/12121] Preserve link redirect counts when updating from 3.0.x.

PHPBB3-12121
Merge pull request #2318 from prototech/ticket/12121

[ticket/12121] Preserve link redirect counts when updating from 3.0.x.

* prototech/ticket/12121:
  [ticket/12121] Preserve link redirect counts when updating from 3.0.x.