[ticket/12615] Fixed inproper clearing of .topic-actions

PHPBB3-12615
[ticket/12541] Activate attachments tab when files are dropped into textarea

PHPBB3-12541
[ticket/12565] Empty anchors introduce white-space in IE11

PHPBB3-12565
[ticket/12521] Fix MCP merge topics row overflow

PHPBB3-12521
Merge pull request #2536 from PayBas/ticket/12521

[ticket/12521] Fix MCP merge topics row overflow
Merge remote-tracking branch 'PayBas/ticket/12565' into develop-ascraeus

* PayBas/ticket/12565:
  [ticket/12565] Empty anchors introduce white-space in IE11
Merge remote-tracking branch 'PayBas/ticket/12615' into develop-ascraeus

* PayBas/ticket/12615:
  [ticket/12615] Fixed inproper clearing of .topic-actions
Merge remote-tracking branch 'PayBas/ticket/12541' into develop-ascraeus

* PayBas/ticket/12541:
  [ticket/12541] Activate attachments tab when files are dropped into textarea

Conflicts:
	phpBB/styles/prosilver/template/forum_fn.js
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12521] Fix MCP merge topics row overflow
  [ticket/12565] Empty anchors introduce white-space in IE11
  [ticket/12541] Activate attachments tab when files are dropped into textarea
  [ticket/12615] Fixed inproper clearing of .topic-actions