Avant Browser 2013 Build 21

- [Update]firefox engine:19.0.2
- [update]chrome engine:25.0.1364.160
- [Fix]print preview problem under IE engine
- [Fix]roboform:couldn't fill form using content menu
- [Fix]some focus problem
- [Fix]close tab problem when using different ways to open tabs
- [Fix]Avant covered the taskbar when in maximize state
- [Fix]Avant frame did not respond under certain situation
- [Fix]link tooltip didn't show up sometimes under IE engine
- [Fix]three buttons missed under full screen/desktop mode
- [Fix]detach tab problem
- [Fix]the auto hided taskbar didn't pop up sometimes
- [Fix]taskbar didn't pop up when pressing Windows key under full screen mode