Add the resource limiting code back to Apache 2.0. This only works on

Unix because I can't find any other platforms with rlimit.  If there are
other platforms that need this code, then some of the code needs to move.
This has just barely been tested, so it could probably use some good
testing.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@85449 13f79535-47bb-0310-9956-ffa450edef68