mod_logio: new format-specifier %C (combined) which is the sum of received and...

mod_logio: new format-specifier %C (combined) which is the sum of received and sent byte counts. PR54015

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1484910 13f79535-47bb-0310-9956-ffa450edef68