patch 9.0.1521: failing redo of command with control characters

Problem:    Failing redo of command with control characters.
Solution:   Use AppendToRedobuffLit() for colon commands. (closes #12354)
diff --git a/src/ops.c b/src/ops.c
index 4c64e05..d46a049 100644
--- a/src/ops.c
+++ b/src/ops.c
@@ -3701,7 +3701,10 @@
 		    ResetRedobuff();
 		else
 		{
-		    AppendToRedobuffSpec(repeat_cmdline);
+		    if (cap->cmdchar == ':')
+			AppendToRedobuffLit(repeat_cmdline, -1);
+		    else
+			AppendToRedobuffSpec(repeat_cmdline);
 		    AppendToRedobuff(NL_STR);
 		    VIM_CLEAR(repeat_cmdline);
 		}