Cleanup APR header files a bit. Basically, this splits ap_table_t related

functions into their own header file, away from apr_pools.h.  At the same
time as I was doing this, I removed a couple of definitions that aren't
used anywhere anymore, like ap_child_info_t.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@85473 13f79535-47bb-0310-9956-ffa450edef68