Submitted by: Jim Jagielski

Do make the code a bit clearer, some minor #define changes (and
the resultant flow-thru in the docs).

   SAFE_UNSERIALIZED_ACCEPT  ->   SINGLE_LISTEN_UNSERIALIZED_ACCEPT
   HAVE_MMAP                 ->   USE_MMAP_SCOREBOARD
   HAVE_SHMGET               ->   USE_SHMGET_SCOREBOARD


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@79959 13f79535-47bb-0310-9956-ffa450edef68