* Simplified barcentric method by only performing the inclusion test once, then broadcasting the results
* Used firstbitlow to simplify 'firstAlive' test (I expect there's an even simpler way, but it's currently eluding me)
* Added a third variant, as suggested by Andy Lauritzen, which uses SV_Coverage instead of a manual inclusion test!
* Note: please turn a blind eye to the rampant code duplication!
Tidied up method 3