New extension callback features.

Support separate parse and add callback arguments.
Add new callback so an application can free extension data.
Change return value for send functions so < 0 is an error 0
omits extension and > 0 includes it. This is more consistent
with the behaviour of other functions in OpenSSL.

Modify parse_cb handling so <= 0 is an error.

Make SSL_CTX_set_custom_cli_ext and SSL_CTX_set_custom_cli_ext argument
order consistent.

NOTE: these changes WILL break existing code.

Remove (now inaccurate) in line documentation.
Reviewed-by: Emilia Käsper <emilia@openssl.org>

ssl/ssl_rsa.c

@@ -921,8 +921,10 @@ static int serverinfo_process_buffer(const unsigned char *serverinfo,
 		/* Register callbacks for extensions */
 		ext_type = (serverinfo[0] << 8) + serverinfo[1];
 		if (ctx && !SSL_CTX_set_custom_srv_ext(ctx, ext_type, 
-						       serverinfo_srv_parse_cb,
-						       serverinfo_srv_add_cb, NULL))
+						       serverinfo_srv_add_cb,
+						       NULL, NULL,
+						       serverinfo_srv_parse_cb, 
+						       NULL))
 			return 0;
 
 		serverinfo += 2;