LSM search has to look up a key's value when it does non-overwrite inserts
and/or upates because it's looking for deleted records and that's flagged
in the value.  Don't overwrite the application's WT_ITEM value and avoid
any possibility of leaking memory.  Reference #965.
Support zero-length data items in LSM, reference #540.
Simplify the change to not overwrite &cursor->value in LSM lookups.

refs #966
Merge pull request #966 from wiredtiger/lsm-use-local-value

overwriting/leaking the application's WT_ITEM value
Merge branch 'develop' into lsm-empty-value

Conflicts:
	src/lsm/lsm_cursor.c
Encode empty values as empty in LSM trees.

refs #540, #966, #968.
Use empty values in LSM indices.

refs #540
Merge pull request #968 from wiredtiger/lsm-empty-value

Support zero-length data items in LSM, reference #540.
LSM cursors are expected to return the tombstone value when used in merges and Bloom filter creation.

refs #540
typo
typo