http: Allow to request system defined CAs for TLS.
* dirmngr/http.h (HTTP_FLAG_TRUST_DEF, HTTP_FLAG_TRUST_SYS): New. * dirmngr/http.c (http_session_new): Add arg "flags". * dirmngr/ks-engine-hkp.c (send_request): Use new flag HTTP_FLAG_TRUST_DEF for the new arg of http_session_new. * dirmngr/ks-engine-http.c (ks_http_fetch): Ditto. * dirmngr/t-http.c (main): Ditto.
- Signed-off-by: Werner Koch <wk@gnupg.org>