function compareMessagesByFixRange(a, b) {
	return a.fix.range[0] - b.fix.range[0] || a.fix.range[1] - b.fix.range[1];
}
Compares items in a messages array by range.
@param {Message} a The first message.
@param {Message} b The second message.
@returns {number} -1 if a comes before b, 1 if a comes after b, 0 if equal.
@private