Another iteration in getting POOL_DEBUG to work correctly. It turns out

there are many more subtle interactions caused by the mod_negotiation
"fast redirect".  So I added an API "hint" function pool_join()... which
is normally a nop, but if POOL_DEBUG is defined this tells the debugging
code that the sub pool is guaranteed to exist as long as the parent
pool does.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@80035 13f79535-47bb-0310-9956-ffa450edef68