[ticket/12991] Have events after/before "add warning" field - user and post

PHPBB3-12991
[ticket/12991] Correct language mistakes

PHPBB3-12991
Merge pull request #2887 from Pico/ticket/12991

[ticket/12991] Have events after/before "add warning" field - user and post
Merge branch 'develop-ascraeus' into develop

Conflicts:
	phpBB/styles/subsilver2/template/mcp_warn_post.html
	phpBB/styles/subsilver2/template/mcp_warn_user.html