patch 9.0.1150: :interface is not implemented yet

Problem:    :interface is not implemented yet.
Solution:   Implement the basics of :interface.
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 1f26437..d8e4ae6 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -991,7 +991,7 @@
     int save_KeyTyped = KeyTyped;
     KeyTyped = FALSE;
 
-    ufunc = define_function(eap, lambda_name, lines_to_free, FALSE);
+    ufunc = define_function(eap, lambda_name, lines_to_free, 0);
 
     KeyTyped = save_KeyTyped;