[ticket/13009] Remove legacy browser hacks

PHPBB3-13009
[ticket/13058] Add min value to jump to page input

PHPBB3-13058
Merge remote-tracking branch 'Nicofuma/ticket/13058' into develop-ascraeus

* Nicofuma/ticket/13058:
  [ticket/13058] Add min value to jump to page input
Merge remote-tracking branch 'hanakin/ticket/13009' into develop-ascraeus

* hanakin/ticket/13009:
  [ticket/13009] Remove legacy browser hacks
[ticket/13040] Fix W3C validator warning in overall_footer.html

Added a non-breaking space to remove the following warning:
**Empty heading.**

```html
<h3 class="alert_title"></h3><p class="alert_text"></p>
```

PHPBB3-13040
Merge remote-tracking branch 'prototech/ticket/13040' into develop-ascraeus

* prototech/ticket/13040:
  [ticket/13040] Fix W3C validator warning in overall_footer.html
[ticket/13065] Fix rehashing of stored password hash in phpBB2 convertor.

PHPBB3-13065
[ticket/13019] Always accept a reason for deleting a post/topic.

PHPBB3-13019
[ticket/13019] Rename deletion reason label.

PHPBB3-13019
[ticket/13019] Do not hide reason field when deleting permanently.

PHPBB3-13019
Merge pull request #2955 from prototech/ticket/13065

[ticket/13065] Fix rehashing of stored password hash in phpBB2 convertor.
Merge pull request #2956 from prototech/ticket/13019

[ticket/13019] Always accept a reason for deleting a post/topic.

* prototech/ticket/13019:
  [ticket/13019] Do not hide reason field when deleting permanently.
  [ticket/13019] Rename deletion reason label.
  [ticket/13019] Always accept a reason for deleting a post/topic.