Referenced the gnutls_load_file() function in the HTTPs examples.

src/examples/demo_https.c

@@ -972,6 +972,8 @@ main (int argc, char *const *argv)
 			MHD_OPTION_CONNECTION_TIMEOUT, (unsigned int) (120 /* seconds */),
 			MHD_OPTION_THREAD_POOL_SIZE, (unsigned int) NUMBER_OF_THREADS,
 			MHD_OPTION_NOTIFY_COMPLETED, &response_completed_callback, NULL,
+			/* Optionally, the gnutls_load_file() can be used to
+			   load the key and the certificate from file. */
 			MHD_OPTION_HTTPS_MEM_KEY, srv_signed_key_pem,
 			MHD_OPTION_HTTPS_MEM_CERT, srv_signed_cert_pem,
 			MHD_OPTION_END);