Allow modules to specify their own logging format specifier. Basically,

mod_log_config has registered an optional function, that other modules
can use to specify a function to be called.  This is analogous to the way
that mod_include works.  This also allows http to do the connection
logging itself, without exposing HTTP specific pieces to other modules.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@88888 13f79535-47bb-0310-9956-ffa450edef68