Interleaved Prune hash/compute methods for clarity.

It's a lot easier to verify they're correct as a pair when you can see them side by side.
Interleaved Isolate hash/compute methods for clarity.

It's a lot easier to verify they're correct as a pair when you can see them side by side.
Fixed poor performance of Prune/Isolate in presence of SetFilter.

Due to an inaccurate hash, we were repeatedly computing the globals every time the SetFilter requested them. Not doing that is quicker.
Merge pull request #1061 from johnhaddon/globalsHashes

Fixed poor performance of Prune/Isolate in presence of SetFilter