Fixed dice rolling.

Added game modes MODE_ROLL1 and MODE_ROLL2 to represent the dice rolling
phases that occur during setup. Dice now roll between 0 and 35,
correctly representing the probability of rolling a given number. The
number now correctly identifies a player, by using the formula
r-((r-1)-((r-1)%4))-1 to convert the roll 'r' into a player ID between 0
and 3.