Refactor to simplify support for non-blocking IO across all HTTP
connectors

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1478017 13f79535-47bb-0310-9956-ffa450edef68
Simplify

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1478034 13f79535-47bb-0310-9956-ffa450edef68
Better comment

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1478035 13f79535-47bb-0310-9956-ffa450edef68
Make inner class static

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1478036 13f79535-47bb-0310-9956-ffa450edef68
Pull up NB_WRITE_INTEREST

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1478037 13f79535-47bb-0310-9956-ffa450edef68