add some debug logging to show more information about passing of sockets

between parent and child

the extra info is helpful when using a generic listener on an IPv6-
enabled box when either IPV6_V6ONLY isn't defined for the APR build
or httpd is built with IPv4-mapped addresses enabled 

in that case you'll see the parent writing one socket but the child
expecting too, before it bails out with

(OS 109)The pipe has been ended.  : Child: Unable to read socket data 
from parent


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1091421 13f79535-47bb-0310-9956-ffa450edef68