Improved automatic keyboard and mouse capture

[Brandon]

Currently, vbox captures the keyboard when a vbox guest window is active and ignores the keyboard when a vbox guest is not the active window. VMWare automatically captures the keyboard when the mouse enters the guest display area regardless of whether the window is active or not and releases it when the mouse leaves the guest display area. The VMWare behavior allows for better integration of the virtual machine into the host environment and would be nice to have in vbox.

It would also be nice to capture all keyboard input when the guest has captured the keyboard so that special combinations, such as Ctrl+Alt+F1, don't need a special host key combination to work. This is especially important in fullscreen mode where only the host+Home or host+F combination should be passed to the host (IMHO).