Hook OBS Info into Demos

[CHILLYBUS]

Currently, pausing a demo with the pause key shows a skill level and hostages rescued. Being able to see various statistics up to that point such as the kill graph (is that in Retro?) or aim % or damage dealt/received or 'best weapon' or 'missiles picked up/fired' would be interesting.

[roncli]

An interesting idea, but I think this'll probably need to be post-1.4. Changes to the demo system aren't easy.