m4: Introduce STABLE_ORDERING_JANSSON

Add a second check for Jansson >= 2.8, which includes
fixes to preserve ordering of object keys.

Use this constant to guard tests that depend on stable ordering.

Signed-off-by: Ján Tomko <jtomko@redhat.com>

tests/virnetdaemontest.c

@@ -375,6 +375,11 @@ mymain(void)
     int ret = 0;
     const char *server_names[] = { "testServer0", "testServer1" };
 
+# if !WITH_STABLE_ORDERING_JANSSON
+    fputs("libvirt not compiled with recent enough Jansson, skipping this test\n", stderr);
+    return EXIT_AM_SKIP;
+# endif
+
     if (virInitialize() < 0 ||
         virEventRegisterDefaultImpl() < 0) {
         virDispatchError(NULL);