- Replace raw slice comparison with a call to user comparator.
  Added test for custom comparators.

- Fix end of namespace comments.

- Fixed bug in picking inputs for a level-0 compaction.

  When finding overlapping files, the covered range may expand
  as files are added to the input set.  We now correctly expand
  the range when this happens instead of continuing to use the
  old range.  For example, suppose L0 contains files with the
  following ranges:

      F1: a .. d
      F2:    c .. g
      F3:       f .. j

  and the initial compaction target is F3.  We used to search
  for range f..j which yielded {F2,F3}.  However we now expand
  the range as soon as another file is added.  In this case,
  when F2 is added, we expand the range to c..j and restart the
  search.  That picks up file F1 as well.

  This change fixes a bug related to deleted keys showing up
  incorrectly after a compaction as described in Issue 44.

(Sync with upstream @25072954)

- Fix for issue 33 (non-null-terminated result from
  leveldb_property_value())

- Support for running multiple instances of a benchmark in parallel.

- Reduce lock contention on Get():
  (1) Do not hold the lock while searching memtables.
  (2) Shard block and table caches 16-ways.

  Benchmark for evaluating this change:
  $ db_bench --benchmarks=fillseq1,readrandom --threads=$n
  (fillseq1 is a small hack to make sure fillseq runs once regardless
  of number of threads specified on the command line).



git-svn-id: https://leveldb.googlecode.com/svn/trunk@49 62dab493-f737-651d-591e-8d6aee1b9529

git-svn-id: https://leveldb.googlecode.com/svn/trunk@23 62dab493-f737-651d-591e-8d6aee1b9529

git-svn-id: https://leveldb.googlecode.com/svn/trunk@21 62dab493-f737-651d-591e-8d6aee1b9529

git-svn-id: https://leveldb.googlecode.com/svn/trunk@20 62dab493-f737-651d-591e-8d6aee1b9529

git-svn-id: https://leveldb.googlecode.com/svn/trunk@18 62dab493-f737-651d-591e-8d6aee1b9529

git-svn-id: https://leveldb.googlecode.com/svn/trunk@2 62dab493-f737-651d-591e-8d6aee1b9529