Invent new structure and associated methods to handle config file

reading. Add "custom" hook to use config file cfg_getline() on
something which is not a FILE
Reviewed by:	Paul +1, Dean +1


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@79468 13f79535-47bb-0310-9956-ffa450edef68