New macro to set some trivially true properties on a BAT: - when a BAT is empty or has a single tuple, both the head and tail   columns are sorted, are key, and (if OID) are dense. - when a BAT is marked dense, it is also sorted.
New macro to set some trivially true properties on a BAT:
- when a BAT is empty or has a single tuple, both the head and tail
  columns are sorted, are key, and (if OID) are dense.
- when a BAT is marked dense, it is also sorted.

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