TupleBuckets in Riak objects

Adds support with test for tuplebuckets in Riak keys.

This exposed that there was no filter using the seglist on the in-mmemory keys.  This means that if there is no filter applied in the fold_function, many false positives may emerge.

This is probably not a big performance benefit (and indeed for performance it may be better to apply during the leveled_pmem:merge_trees).

Some thought still required as to what is more likely to contribute to future bugs: an extra location using the hash matching found in leveled_sst, or the extra results in the query.

src/leveled_codec.erl

@@ -36,6 +36,7 @@
         inker_reload_strategy/1,
         strip_to_seqonly/1,
         strip_to_statusonly/1,
+        strip_to_segmentonly/1,
         strip_to_keyseqonly/1,
         strip_to_indexdetails/1,
         striphead_to_v1details/1,
@@ -174,12 +175,24 @@ segment_hash(Key) when is_binary(Key) ->
 segment_hash({?RIAK_TAG, Bucket, Key, null}) 
                                     when is_binary(Bucket), is_binary(Key) ->
     segment_hash(<<Bucket/binary, Key/binary>>);
+segment_hash({?RIAK_TAG, {BucketType, Bucket}, Key, SubKey})
+                            when is_binary(BucketType), is_binary(Bucket) ->
+    segment_hash({?RIAK_TAG,
+                    <<BucketType/binary, Bucket/binary>>,
+                    Key,
+                    SubKey});
 segment_hash({?HEAD_TAG, Bucket, Key, SubK})
                     when is_binary(Bucket), is_binary(Key), is_binary(SubK) ->
     segment_hash(<<Bucket/binary, Key/binary, SubK/binary>>);
 segment_hash({?HEAD_TAG, Bucket, Key, _SubK})
                                     when is_binary(Bucket), is_binary(Key) ->
     segment_hash(<<Bucket/binary, Key/binary>>);
+% segment_hash({?HEAD_TAG, {BucketType, Bucket}, Key, SubKey})
+%                             when is_binary(BucketType), is_binary(Bucket) ->
+%     segment_hash({?HEAD_TAG,
+%                     <<BucketType/binary, Bucket/binary>>, 
+%                     Key,
+%                     SubKey});
 segment_hash(Key) ->
     segment_hash(term_to_binary(Key)).
 
@@ -207,6 +220,9 @@ strip_to_statusonly({_, V}) -> element(2, V).
 -spec strip_to_seqonly(ledger_kv()) -> non_neg_integer().
 strip_to_seqonly({_, V}) -> element(1, V).
 
+-spec strip_to_segmentonly(ledger_kv()) -> segment_hash().
+strip_to_segmentonly({_LK, LV}) -> element(3, LV).
+
 -spec strip_to_keyseqonly(ledger_kv()) -> {ledger_key(), integer()}.
 strip_to_keyseqonly({LK, V}) -> {LK, element(1, V)}.