In ErrorLogFormat, make it possible to log an item only if the loglevel

of the message is higher than a specified value. This allows to achive
the old behaviour for the source file name/line number of being only
logged for debug and higher.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1001381 13f79535-47bb-0310-9956-ffa450edef68