Fix spectator list not compensating for non-green resolutions

The spectator list at the bottom of the scoreboard on ringslinger gametypes had their text appear and disappear within the boundaries of the screen on non-green resolutions. This patch compensates for that by calculating text visibility relative to the actual screen resolution rather than the base resolution.

I also went ahead and removed a bunch of complexity within that function, since it does a lot of string juggling to stop drawing characters as soon as they go off-screen, something that looks like an optimization but dubious since the scoreboard is not even remotely a bottleneck and the performance loss caused by copying strings most likely counteracts the performance gain.