Implement new ScoreBoardFile directive logic. This affects how we

create the scoreboard's shared memory segment. We now have the best of
both worlds:

if config specifies ScoreBoardFile
  create name-based shared memory, errors are fatal
else /* we get to choose */
  create anonymous shared memory
  if ENOTIMPL
    create name-based shared memory from DEFAULT_SCOREBOARD
  else
    errors are fatal

This gives us the flexibility to have anonymous shared memory (on platforms
that support it) as well as name-based shared memory when third-party
programs want access to our scoreboard.

The ap_scoreboard_fname static variable is now owned by the scoreboard.c
file, and no longer by the MPMs. The MPMs MUST NOT set ap_scoreboard_fname
to a default, since that will override the default creation logic and
only allow name-based segments.

Submitted by:	Aaron Bannert
Reviewed by:	Justin Erenkrantz


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93434 13f79535-47bb-0310-9956-ffa450edef68