"final" is now a reserved word, so change occurrences to "finalize".
Merge pull request #75 from kinghajj/change-final-to-finalize

"final" is now a reserved word, so change occurrences to "finalize".
Prepare for s/static/const/
Merge pull request #78 from alexcrichton/update

Prepare for s/static/const/
Better thread working

Works pretty stable for me, although I'm not sure it is 100% thread safe yet.

Changes mostly inspired by https://www.arangodb.org/2014/07/08/started-hate-openssl :

- Switched to newer CRYPTO_THREADID API for Unixes

- Clearing errors queue before every critical operation
Simplified SslStream.write, updated comments
Locking internal buffer from same thread access

If cloned stream was used in the same thread
WIP: erase later