rend: add configure option

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/main@10585 ddefafc4-47db-0310-ae44-fa13212b10f2
travis: configure --with-rend

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/main@10586 ddefafc4-47db-0310-ae44-fa13212b10f2