patch 8.2.1978: making a mapping work in all modes is complicated

Problem:    Making a mapping work in all modes is complicated.
Solution:   Add the <Cmd> special key. (Yegappan Lakshmanan, closes #7282,
            closes 4784, based on patch by Bjorn Linse)
diff --git a/src/screen.c b/src/screen.c
index b204de9..7c6fe63 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -4192,7 +4192,8 @@
 #endif
 		    msg_puts_attr(_(" INSERT"), attr);
 		}
-		else if (restart_edit == 'I' || restart_edit == 'A')
+		else if (restart_edit == 'I' || restart_edit == 'i' ||
+			restart_edit == 'a' || restart_edit == 'A')
 		    msg_puts_attr(_(" (insert)"), attr);
 		else if (restart_edit == 'R')
 		    msg_puts_attr(_(" (replace)"), attr);