merkle: Refactor snapshotConsistency function (#2163)
merkle: Refactor snapshotConsistency function (#2163)

- Don't allocate memory for the empty case.
- Replace the loop of integer shifts by a single line that counts bits in one go.
- Convert to uint/uint64 asap.
AlCutter/trillian,gdbelvin/trillian,AlCutter/trillian,google/trillian,gdbelvin/trillian,google/trillian,gdbelvin/trillian