mod_proxy_balancer,mod_slotmem_shm: Rework SHM reuse/deletion to not

depend on the number of restarts (non-Unix systems) and preserve shared
names as much as possible on configuration changes for SHMs and persisted
files.  PR 62044.
trunk patch: http://svn.apache.org/r1822509
             http://svn.apache.org/r1822511
             http://svn.apache.org/r1823412
             http://svn.apache.org/r1823415
             http://svn.apache.org/r1823416
             http://svn.apache.org/r1823564
             http://svn.apache.org/r1823572
             http://svn.apache.org/r1823575
2.4.x patch: trunk works (modulo CHANGES)
             (or http://home.apache.org/~ylavic/patches/httpd-2.4.x-PR62044-slotmems_reuse.patch)
+1: ylavic, jim, minfrin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1824180 13f79535-47bb-0310-9956-ffa450edef68