valgrind.supp: add the event-based call stack-trace too

Without this, test 165 triggers a valgrind error when ran with
curl_easy_perform_ev

tests/valgrind.supp

@@ -14,3 +14,24 @@
    fun:operate
    fun:main
 }
+
+{
+   libidn-idna_to_ascii-error-eventbased
+   Memcheck:Addr4
+   fun:idna_to_ascii_4z
+   fun:idna_to_ascii_8z
+   fun:idna_to_ascii_lz
+   fun:fix_hostname
+   fun:resolve_server
+   fun:create_conn
+   fun:Curl_connect
+   fun:multi_runsingle
+   fun:multi_socket
+   fun:curl_multi_socket_action
+   fun:wait_or_timeout
+   fun:easy_events
+   fun:easy_perform
+   fun:curl_easy_perform_ev
+   fun:operate
+   fun:main
+}