patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient

Problem:    Vim9: concatenating lines with backslash is inconvenient.
Solution:   Support concatenating lines starting with '|', useful for
            :autocmd, :command, etc. (closes #6702)
diff --git a/src/structs.h b/src/structs.h
index a6cd346..ba42e33 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1565,7 +1565,8 @@
 // type of getline() last argument
 typedef enum {
     GETLINE_NONE,	    // do not concatenate any lines
-    GETLINE_CONCAT_CONT,    // concatenate continuation lines
+    GETLINE_CONCAT_CONT,    // concatenate continuation lines in Vim9 script
+    GETLINE_CONCAT_CONTDEF, // concatenate continuation lines always
     GETLINE_CONCAT_ALL	    // concatenate continuation and Vim9 # comment lines
 } getline_opt_T;