Extend serf_get to allow HEAD requests without a protocol error.
Extend serf_get to allow HEAD requests without a protocol error.

* test/serf_get.c
  (app_baton_t): Add variable.
  (accept_response): For head requests, mark that no body is expected
     This matches how Subversion's libsvn_ra_serf marks this kind of requests.
  (main): Detect head request.

jandre/serf,jandre/serf,jandre/serf,jandre/serf