Fix possible memory leak with NIO when executor needs to create a new
thread.
Pull up common code.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1519991 13f79535-47bb-0310-9956-ffa450edef68
Add some plumbing for non-blocking writes to the AJP connectors. There
is no functional change. All writes remain blocking.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1519994 13f79535-47bb-0310-9956-ffa450edef68