(BS2000 only)

Update BS2000 OS code to work with recent versions. Starting with
release A17, the child fork() must be replaced by a _rfork().


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@82326 13f79535-47bb-0310-9956-ffa450edef68