Forward local IP address as a custom request attribute

Forward local IP address as a custom request attribute
like we already do for the remote port.

Both were forgotten in the original AJP 13 spec
but are needed by the Servlet spec. Until now,
Tomcat simply returns for getLocalAddr() the same as
for getLocalName().

The next round of Tomcat releases will look for the
optional new request attribute.

See also Tomcat BZ 56661.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1610207 13f79535-47bb-0310-9956-ffa450edef68