Add a post-level statistics display

[Nami Verasche]

http://www.lemmingsforums.net/index.php?topic=2376.0

NeoLemmix previously had a scoring system (now removed). The suggestion is to give more detailed, purely-objective statistics.

[Nami Verasche]

Fixed bug #3 from this topic: https://www.lemmingsforums.net/index.php?topic=4251.0 Also, in general, did a bit of tidyup on the gameplay-pause-and-mouse-release-when-showing-child-window code in GameWindow.

→ <<cset 1a69b6a97d7b>>

[Nami Verasche]

Fixed bug #3 from this topic: https://www.lemmingsforums.net/index.php?topic=4251.0 Also, in general, did a bit of tidyup on the gameplay-pause-and-mouse-release-when-showing-child-window code in GameWindow.

→ <<cset 034f3df8fe4b>>