patch 8.0.1427: the :leftabove modifier doesn't work for :copen

Problem:    The :leftabove modifier doesn't work for :copen.
Solution:   Respect the split modifier. (Yegappan Lakshmanan, closes #2496)
diff --git a/src/quickfix.c b/src/quickfix.c
index 05e5946..8e74521 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -3222,6 +3222,8 @@
     }
     else
     {
+	int flags = 0;
+
 	qf_buf = qf_find_buf(qi);
 
 	/* The current window becomes the previous window afterwards. */
@@ -3229,10 +3231,14 @@
 
 	if ((eap->cmdidx == CMD_copen || eap->cmdidx == CMD_cwindow)
 		&& cmdmod.split == 0)
-	    /* Create the new window at the very bottom, except when
+	    /* Create the new quickfix window at the very bottom, except when
 	     * :belowright or :aboveleft is used. */
 	    win_goto(lastwin);
-	if (win_split(height, WSP_BELOW | WSP_NEWLOC) == FAIL)
+	/* Default is to open the window below the current window */
+	if (cmdmod.split == 0)
+	    flags = WSP_BELOW;
+	flags |= WSP_NEWLOC;
+	if (win_split(height, flags) == FAIL)
 	    return;		/* not enough room for window */
 	RESET_BINDING(curwin);