Now that LUCENE-1516 is close to being committed perhaps we can
figure out the priority of other issues:

1. Searchable IndexWriter RAM buffer

2. Finish up benchmarking and perhaps implement passing
filters to the SegmentReader level

3. Deleting by doc id using IndexWriter

With 1) I'm interested in how we will lock a section of the
bytes for use by a given reader? We would not actually lock
them, but we need to set aside the bytes such that for example
if the postings grows, TermDocs iteration does not progress to
beyond it's limits. Are there any modifications that are needed
of the RAM buffer format? How would the term table be stored? We
would not be using the current hash method?