Restore small message window with wide sidebar [CR]

As KA101 does not seem to be happy with the extended message window, this is a different implementation that restores the original message window height (20 line). The whole PR only affects the game with wide sidebar.

It uses the `w_status2` window to clear the space below the message (and status and location) window, this keeps the fix for #9834 (w_status2 clears that part of the screen). The issue #2091 should than be reopened because w_status2 does not contain anything and the lower right part of the screen is again wasted.

Or, if you're happy with the current state, close this. Choose wisely.