* 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.
sufficient to turn the feature on. (http_open): From here.
(http_document): And here.
* gpgkeys_hkp.c (srv_replace): New function to transform a SRV
hostname to a real hostname. (main): Call it from here for the
HAVE_LIBCURL case (without libcurl is handled via the curl-shim).
* curl-shim.h, curl-shim.c (curl_easy_setopt, curl_easy_perform): Add
a CURLOPT_SRVTAG_GPG_HACK (passed through the the http engine).
number options are passed as long.
* curl-shim.c (curl_easy_setopt): Minor tweak to match the real curl
better - libcurl uses 'long', not 'unsigned int'.
* gpgkeys_curl.c (main): Use curl_version_info to verify that the
protocol we're about to use is actually available.
* curl-shim.h, curl-shim.c (curl_free): Make into a macro.
(curl_version_info): New. Only advertises "http" for our shim, of
course.
