Maxthon 3.4.3.1800 Beta

# New Features:
* Added "Extension List" into "MX Cloud Sync" center
# Fixes:
* Main Frame
- Browser language setting problem
- Keywords displayed different in Multiple Search Box and in page search box
- Page search box did not hide in Retro Mode
- Browser languages loading problem
- Tab Sync problem
- No response problem
- Input method input box display problem
- The right-click menu of Quick App icons in Task Bar could not disappear
* Webkit Core > Some crash problems caused be WebGL
- Highlight of "Find in Page" did not work
- Improved the support for HTML5 Notifications
- Fixed freeze and progress remain problem when closed the browser
* Extension Platform
- Improved Extension Platform