Byte Lane Enables

Really this should be a bool[] to match the unsigned char[], but the conclusion is that is it only small bus transfers that encode their byte lane enables. If this is wrong, then a user defined type would be needed.

Hence the type for byte lane enable is uint64, with each bit representing an enable for each of the bytes in the data from byte lane enable bit 0 being the enable for index[0].

(We should possibly re-think this, and use a bool vector, and allocate it along side the data.... )