patch 8.2.3782: Vim9: no error if a function shadows a script variable

Problem:    Vim9: no error if a function shadows a script variable.
Solution:   Check the function doesn't shadow a variable. (closes #9310)
diff --git a/src/vim.h b/src/vim.h
index c4f6f15..6427380 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2782,6 +2782,7 @@
 #define EVAL_VAR_VERBOSE	1   // may give error message
 #define EVAL_VAR_NOAUTOLOAD	2   // do not use script autoloading
 #define EVAL_VAR_IMPORT		4   // may return special variable for import
+#define EVAL_VAR_NO_FUNC	8   // do not look for a function
 
 // Maximum number of characters that can be fuzzy matched
 #define MAX_FUZZY_MATCHES	256