patch 8.1.0306: plural messages are not translated properly

Problem:    Plural messages are not translated properly.
Solution:   Add more usage of NGETTEXT(). (Sergey Alyoshin)
diff --git a/src/misc1.c b/src/misc1.c
index 1647aa9..f2aa96b 100644
--- a/src/misc1.c
+++ b/src/misc1.c
@@ -3802,24 +3802,12 @@
 
     if (pn > p_report)
     {
-	if (pn == 1)
-	{
-	    if (n > 0)
-		vim_strncpy(msg_buf, (char_u *)_("1 more line"),
-							     MSG_BUF_LEN - 1);
-	    else
-		vim_strncpy(msg_buf, (char_u *)_("1 line less"),
-							     MSG_BUF_LEN - 1);
-	}
+	if (n > 0)
+	    vim_snprintf((char *)msg_buf, MSG_BUF_LEN,
+		    NGETTEXT("%ld more line", "%ld more lines", pn), pn);
 	else
-	{
-	    if (n > 0)
-		vim_snprintf((char *)msg_buf, MSG_BUF_LEN,
-						     _("%ld more lines"), pn);
-	    else
-		vim_snprintf((char *)msg_buf, MSG_BUF_LEN,
-						    _("%ld fewer lines"), pn);
-	}
+	    vim_snprintf((char *)msg_buf, MSG_BUF_LEN,
+		    NGETTEXT("%ld line less", "%ld fewer lines", pn), pn);
 	if (got_int)
 	    vim_strcat(msg_buf, (char_u *)_(" (Interrupted)"), MSG_BUF_LEN);
 	if (msg(msg_buf))