Fix a regression in SslHandler where delegated tasks run in a different executor makes the session hang

- Fixes #2098
Fix Java 5 source compatibility issue / Inspector warnings
Deprecate specifying an alternative Executor for delegated tasks for SslHandler / Fix a problem where SslHandler consumes too much CPU until the delegated task is finished.
Issue# 2077
Potential issues in Netty 3.8's Spdy implementation?
https://github.com/netty/netty/issues/2077