patch 9.0.1588: Incsearch not triggered when pasting clipboard register

Problem:    Incsearch not triggered when pasting clipboard register on the
            command line.
Solution:   Also set "literally" when using a clipboard register. (Ken Takata,
            closes #12460)
diff --git a/src/ex_getln.c b/src/ex_getln.c
index fbda2cc..00d3292 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -1221,7 +1221,12 @@
 #endif
     if (c != ESC)	    // use ESC to cancel inserting register
     {
-	literally = i == Ctrl_R;
+	literally = i == Ctrl_R
+#ifdef FEAT_CLIPBOARD
+			|| (clip_star.available && c == '*')
+			|| (clip_plus.available && c == '+')
+#endif
+			;
 	cmdline_paste(c, literally, FALSE);
 
 #ifdef FEAT_EVAL