patch 9.0.1354: "gr CTRL-G" stays in virtual replace mode

Problem:    "gr CTRL-G" stays in virtual replace mode. (Pierre Ganty)
Solution:   Prepend CTRL-V before control characters. (closes #12045)
diff --git a/src/normal.c b/src/normal.c
index b3ea5e8..95bb1a9 100644
--- a/src/normal.c
+++ b/src/normal.c
@@ -5033,6 +5033,10 @@
     {
 	if (cap->extra_char == Ctrl_V)	// get another character
 	    cap->extra_char = get_literal(FALSE);
+	if (cap->extra_char < ' ')
+	    // Prefix a control character with CTRL-V to avoid it being used as
+	    // a command.
+	    stuffcharReadbuff(Ctrl_V);
 	stuffcharReadbuff(cap->extra_char);
 	stuffcharReadbuff(ESC);
 	if (virtual_active())