Following up on r1443772, and the debug information from Philip implement a
proper handling of non RFC-compliant location headers in the ra_serf code.

This should fix the segfault on the centos buildbot.

* subversion/libsvn_ra_serf/util.c
  (response_get_location): Add scratch_pool. Make apr produce a full url based
    on a provided base url.
  (handle_response): Pass session url (which is always set) as base url, and
    and a scratch pool to response_get_location.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1443906 13f79535-47bb-0310-9956-ffa450edef68