Backport

  *) mod_slotmem_shm: Add generation number to shm filename to fix races with
                      graceful restarts.  PRs 62044 and 62308.
     trunk patch: https://svn.apache.org/r1831868
                  https://svn.apache.org/r1831869
                  https://svn.apache.org/r1831870
                  https://svn.apache.org/r1831871
                  https://svn.apache.org/r1831872
                  https://svn.apache.org/r1831935
                  https://svn.apache.org/r1831938
                  https://svn.apache.org/r1832479
     2.4.x patch: http://home.apache.org/~ylavic/patches/httpd-2.4.x-balancer_slotmem-v2.patch
     +1: ylavic, jim, druggeri

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1834887 13f79535-47bb-0310-9956-ffa450edef68