dirmngr: Further simplify the http code and improve a message.
* dirmngr/http.c (make_fp_write, make_fp_read): New. (http_raw_connect): Use new functions. (http_wait_response): Ditto. (send_request): Ditto. Change proxy error diagnostic. (connect_server): Improve error message for host not found.
- GnuPG-bug-id: T5768