patch 8.2.5106: default cmdwin mappings are re-mappable

Problem:    Default cmdwin mappings are re-mappable.
Solution:   Make the default mappings not re-mappable. (closes #10580)  Use
            symbols for the first do_map() argument.
diff --git a/src/ex_getln.c b/src/ex_getln.c
index 8be971a..af4dc19 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -4463,8 +4463,8 @@
     {
 	if (p_wc == TAB)
 	{
-	    add_map((char_u *)"<buffer> <Tab> <C-X><C-V>", MODE_INSERT);
-	    add_map((char_u *)"<buffer> <Tab> a<C-X><C-V>", MODE_NORMAL);
+	    add_map((char_u *)"<buffer> <Tab> <C-X><C-V>", MODE_INSERT, TRUE);
+	    add_map((char_u *)"<buffer> <Tab> a<C-X><C-V>", MODE_NORMAL, TRUE);
 	}
 	set_option_value_give_err((char_u *)"ft",
 					       0L, (char_u *)"vim", OPT_LOCAL);