http: Allow overriding of the Host header.

* common/http.c (http_open): Add arg httphost.
(http_open_document): Pass NULL for httphost.
(send_request): Add arg httphost.  If given, use HTTPHOST instead of
SERVER.  Use https with a proxy if requested.
(http_verify_server_credentials): Do not stop at the first error
message.
* dirmngr/ocsp.c (do_ocsp_request): Adjust call to http_open.
* keyserver/curl-shim.c (curl_easy_perform): Ditto.
* dirmngr/ks-engine-http.c (ks_http_fetch): Ditto.
* dirmngr/ks-engine-hkp.c (ks_hkp_help): Ditto.

dirmngr/ks-engine-hkp.c

@@ -765,6 +765,7 @@ send_request (ctrl_t ctrl, const char *request, const char *hostportstr,
   err = http_open (&http,
                    post_cb? HTTP_REQ_POST : HTTP_REQ_GET,
                    request,
+                   NULL,
                    /* fixme: AUTH */ NULL,
                    httpflags,
                    /* fixme: proxy*/ NULL,

dirmngr/ks-engine-http.c

@@ -68,6 +68,7 @@ ks_http_fetch (ctrl_t ctrl, const char *url, estream_t *r_fp)
   err = http_open (&http,
                    HTTP_REQ_GET,
                    url,
+                   /* httphost */ NULL,
                    /* fixme: AUTH */ NULL,
                    0,
                    /* fixme: proxy*/ NULL,

dirmngr/ocsp.c

@@ -165,7 +165,7 @@ do_ocsp_request (ctrl_t ctrl, ksba_ocsp_t ocsp, gcry_md_hd_t md,
     }
 
  once_more:
-  err = http_open (&http, HTTP_REQ_POST, url, NULL,
+  err = http_open (&http, HTTP_REQ_POST, url, NULL, NULL,
                    (opt.honor_http_proxy? HTTP_FLAG_TRY_PROXY:0),
                    opt.http_proxy, NULL, NULL, NULL);
   if (err)

dirmngr/server.c

@@ -298,7 +298,7 @@ skip_options (char *line)
 }
 
 
-/* Return an error if the assuan context does not belong to teh owner
+/* Return an error if the assuan context does not belong to the owner
    of the process or to root.  On error FAILTEXT is set as Assuan
    error string.  */
 static gpg_error_t