Thread pools

[cm...@yahoo.com]

Hi,

The thread pool changes are almost done, with better interfaces and
monitoring and even less coupling ( it no longer uses the Log, but 
generates Events - the only dependency is now JDK1.1 ).

The code is almost the same as functionality ( except for additional
sugar ), and should replace the old one without problems. The main
benefits are the fact that the same pool can be used for all tasks
( http, ajp, session expiry, etc ), and we can better monitor what's
happening inside ( by adding a Listener that will receive notifications 
for all relevant steps ). An admin page will be added later.

Larry - let me know if you are ok with checking it in. I'm confident the
code is as good ( or better ) than before, but this is a very important
component.

We can keep it as an experimental module - in /proposals - and keep the
old code as default. Having fewer threads is not that important.

Another option is to check this in the commons-sandbox workspace. There
are other projects using thread pools, and we may have a chance to share
it and merge it with other ideas. This can be done in paralel - and
if/when the sandbox code is stable we can start using it ( replacing or 
as an alternative to the old thread pool ).

What do you think ? 

I'll probably go ahead and check it in sandbox first, and after a bit
more testing I'll ask for a vote. 

Costin