input/curl: move code to class CurlRequest

The CurlRequest gives us a more low-level API to CURL without the
InputStream interface, integrated into our IOThread.

src/lib/curl/Global.cxx

@@ -179,6 +179,8 @@ CurlGlobal::Remove(CURL *easy)
 	assert(easy != nullptr);
 
 	curl_multi_remove_handle(multi.Get(), easy);
+
+	InvalidateSockets();
 }
 
 static CurlRequest *