Add function inferXOloc() to infer crossover locations from genotype probabilities.
Add function trimXO() for trimming tight double-crossovers from the output of inferXOloc().
Add function randXOloc() for randomizing the estimated crossover locations, uniform within their intervals.
Add functions grabXO() and grab2XO() for grabbing all crossover locations and all pairs of crossovers, when there are exactly two.