Keep pace with DBCP2 changes (just various bits of clean-up)

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1572069 13f79535-47bb-0310-9956-ffa450edef68
WIP NIO2 connector
Fixes and cleanups for input stability.
Fix output corruption for blocking IO.
Fix async (except keepalive after async), non blocking output, deadlocks and stability.