Document recent changes in prefork.c/r1.287:

  "Bump MAX_SERVER_LIMIT by 10x (hoping to stay ahead of Moore's Law
  for a little while) since the current limit is too small for at
  least one high end site."


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@102378 13f79535-47bb-0310-9956-ffa450edef68