patch 8.2.2597: Vim9: "import * as" does not work at script level

Problem:    Vim9: "import * as" does not work at script level.
Solution:   Implement using an imported namespace.
diff --git a/src/vim.h b/src/vim.h
index 5dd69f6..7f4c99a 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2702,4 +2702,9 @@
 #define MCH_DELAY_IGNOREINPUT	1
 #define MCH_DELAY_SETTMODE	2
 
+// Flags for eval_variable().
+#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
+
 #endif // VIM__H