Provide ability to monitor the Executor pool via JMX

In AS 4.0.x it was possible to throttle the number of active threads using the maxSpareThreads attribute
In EAP 4 & 5, based on Tomcat 6, this is no longer possible as the attribute has been removed. The Executor was introduced as the alternative way to control the number of idle threads.

It is currently not possible to monitor executor threads via JMX. This was the case in the early releases of Tomcat 6, but in Tomcat 6.0.26 onwards, you can now do so.

Can the tomcat fix be backported to JBossWeb 2.1.x