ra_serf: Fix segmentation fault when using NTLM or Negotiate authentication.
ra_serf: Fix segmentation fault when using NTLM or Negotiate authentication.

* subversion/libsvn_ra_serf/auth.c
  (handle_auth_header): authn headers do not always use arguments (e.g. NTLM,
   Negotiate). In these cases, just use the header value as is.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion