patch 9.0.0419: the :defer command does not check the function arguments

Problem:    The :defer command does not check the function argument count and
            types.
Solution:   Check the function arguments when adding a deferred function.
diff --git a/src/version.c b/src/version.c
index c3d1ad5..81de0b7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    419,
+/**/
     418,
 /**/
     417,