Merge r778531 from trunk:

Fix IPv6 literal addresses passed to a proxied backend.
PR 47177
Patch by Carlos Garcia Braschi

Submitted by: niq
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@792914 13f79535-47bb-0310-9956-ffa450edef68