improve lerping

[somefnfplayerlol]

[crowplexus]

would be better to use Main.framerateAdjust for the easeLerp, as it's used often on Forever Engine, like this

var easeLerp = 1 - Main.framerateAdjust(0.5);

[Yoshubs]

I'll merge it for now but there's a lot of framerate bound stuff in legacy still that bothers me and I wish I could properly fix it at some point.