patch 8.2.3249: Vim9: error for re-imported function with default argument

Problem:    Vim9: error for re-imported function with default argument.
Solution:   Do not check argument type if it is still unknown. (closes #8653)
diff --git a/src/vim.h b/src/vim.h
index 30cf284..54d507e 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2736,4 +2736,7 @@
 // Maximum number of characters that can be fuzzy matched
 #define MAX_FUZZY_MATCHES	256
 
+// flags for equal_type()
+#define ETYPE_ARG_UNKNOWN 1
+
 #endif // VIM__H