Stop tests failing because nbRead isn't implemented.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1480783 13f79535-47bb-0310-9956-ffa450edef68
Implement non-blocking write for APR.
Add some trace level debug code to AprEndpoint that was useful in getting this working.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1480786 13f79535-47bb-0310-9956-ffa450edef68