seqlock skeleton.
fully using seqlock for leveldb blockchain.
cleanup seqlock fetch read spinlock.
reorg test.
show_chain(blockchain)
don't print block depth for not confirmed blocks.
add comment clarifying sleep inside seqloop loop.
bugfix: race condition in fetch block locator
fix warning in leveldb about initialization order of vars in contrsutctor.
fix to build on mac osx.
mac osx build instructions.