patch 8.0.1378: autoload script sources itself when defining function

Problem:    Autoload script sources itself when defining function.
Solution:   Pass TFN_NO_AUTOLOAD to trans_function_name(). (Yasuhiro
            Matsumoto, closes #2423)
diff --git a/src/userfunc.c b/src/userfunc.c
index 9b60554..580df0b 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -1886,7 +1886,7 @@
      * g:func	    global function name, same as "func"
      */
     p = eap->arg;
-    name = trans_function_name(&p, eap->skip, 0, &fudi, NULL);
+    name = trans_function_name(&p, eap->skip, TFN_NO_AUTOLOAD, &fudi, NULL);
     paren = (vim_strchr(p, '(') != NULL);
     if (name == NULL && (fudi.fd_dict == NULL || !paren) && !eap->skip)
     {