Use a timer to periodically save the current state: which windows are open,
which tabs are open in which window, which one is focused, etc. The
relevant entry in the eet file is updated. This should provide a somewhat
crash-safe approach, which is way better than the previous version.
The timer is currently set to fire every 15s: testing should be performed to
ensure this won't impact performance too much. Should this be a problem,
this interval might be a user-customized setting.
SVN revision: 52522
Leandro Pereira