Fix unused variable warning: db unused.
Remove unused m_pad1 and m_pad2 from UptimeTimer.
Remove unused m_scheduler from NullBackend.
Several small fixups to db_impl.cc:
Reordered init list in DBImpl ctor to reflect ctor order. Opened issue with HyperLevelDB.
Changed %ld to %llu to match type of iters. Already fixed at HyperLevelDB.
Removed unused local i from DBImpl::DoCompactionWork. Opened issue with HyperLevelDB.
Removed unused local allow_delay from SequenceWriteBegin. Opened issue with HyperLevelDB.
Several small fixups to version_set.cc:
Remove useless call to TotalFileSize from PickLevelForMemTableOutput.  Opened issue with HyperLevelDB.
Remove unused local largest from PickCompaction.  Opened issue with HyperLevelDB.
#ifdef out unused function IntSetToString (keep for debugging purposes).  Opened issue with HyperLevelDB.
Remove unused start_at_ from ReplayIteratorImpl.
Opened issue with HyperLevelDB.
Remove const from MultiSocketType::native_handle function
to unhide virtual function in base class.
Fix mangled return statement in PeersImp::findPeerByShortID
Silence unused variable warning in ManagerImp::add.