User:Jens3/xonotic benchmark

The benchmark with -0.8.2 ran on the Pi400 with:

xonotic-glx -benchmark demos/the-big-keybench 2>&1 | egrep -e '[0-9]+ frames' 3859 frames 188.9610292 seconds 20.4222004 fps, one-second fps min/avg/max: 8 22 34 (123 seconds)