v4.0
[bug] Undo/redo don't work under certain context
[bug] For the text annotation, the character spacing is too big when typing alphabets under CJK/IME context.
[bug] NewTab button disappears if too many tabs
[bug] Tabbar bugs
[bug] Edit/Save locked documents
[bug] Save opened URLs (260/256)
[bug] Annotations aren't displayed on certain PDF documents
[bug] Adobe Reader compatibility
