changed compare function to have "unsigned int"
changed compare function to have "unsigned int"

in order to make this compile with clang on FreeBSD 10.
arq5x/bedtools2,jmarshall/bedtools2,jmarshall/bedtools2,arq5x/bedtools2,arq5x/bedtools2,arq5x/bedtools2,arq5x/bedtools2,jmarshall/bedtools2,jmarshall/bedtools2,jmarshall/bedtools2