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

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