First pass at TSM cursor iteration ended up searching the file indexes
too frequently and hurt performance. This changes that to search it once
and then have the cursor hold onto the block locations to seek
to. Doubles the query performance from the first iteration, but still a lot
of room for improvement.
This writes a tombstone file containing a line per deleted key. This
file is read when a TSMReader is created and any keys listed in the file
are removed from the index.
Jason Wilder