Increase the length of the player input buffer

This simply changes the value of BACKUPTICS from 32 to 96 (a little less than 3 seconds), causing the game to buffer inputs for a longer time before freezing.

This should have three main advantages:

1. Players with high latency are less likely to lag everyone else in the server.
2. Players joining during a netgame will pause the game for less long (2 seconds less probably).
3. Short game/internet freezes are less likely to affect everyone else in the server.