Strip the port when caching the host part of URLs

Fixes #888

ChangeLog

@@ -12,6 +12,9 @@ been set to `true`.
  - New command-line option: `-show-certs` to print DoH certificate
 hashes.
  - Solaris packages are now provided.
+ - DoH servers on a non-standard port, with stamps that don't include
+IP addresses, and without working system resolvers can now be properly
+bootstrapped.
 
 * Version 2.0.25
  - The example IP address for network probes didn't work on Windows.

dnscrypt-proxy/xtransport.go

@@ -224,7 +224,7 @@ func (xTransport *XTransport) Fetch(method string, url *url.URL, accept string,
 		req.Body = bc
 	}
 	var err error
-	host := url.Host
+	host := ExtractHost(url.Host)
 	if xTransport.proxyDialer == nil && strings.HasSuffix(host, ".onion") {
 		return nil, 0, errors.New("Onion service is not reachable without Tor")
 	}