Merge r1206268 from trunk:

Allow compile time changes of field sizes and be more
"clear" regarding the diff between balancer and worker slots...
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1206269 13f79535-47bb-0310-9956-ffa450edef68