Increase fun of teleporting 100%; make telefrags more likely

Before: Short-range teleports would take 15 cracks at trying to find a completely empty map space. Even in a Spawn Density 50 city, you'll probably hit an empty space (if you don't die from the zombie mob first).

After: Short-range teleports take 15 cracks a trying to find a map space that's not a wall (as teleporting into a wall is basically instant death - 1d500 torso damage). If there's a mob in the square you're teleporting to, too bad for it. Insert your favorite onomatopaeia here.

I felt this was necessary because you are practically *never* going to see zombie telefrags. Even now, the radius is big enough that it's extremely unlikely, but at least it's not "pretty much impossible" like it was before.