Fixes #2212 Drafts update the forum last post

http://dev.mybb.com/issues/2212
Merge branch 'fix-2212' of https://github.com/JordanMussi/MyBB into JordanMussi-fix-2212
Fixes #333 delete user - thread uid
Fixes #356 Hitting Post Thread when having disallowed attachment ignores all submitted content
Merge remote-tracking branch 'upstream/master'