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/ex_docmd.c b/src/ex_docmd.c
index 14ec213..ccd96b1 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -5749,22 +5749,16 @@
 	    {
 		char_u	buff[DIALOG_MSG_SIZE];
 
-		if (n == 1)
-		    vim_strncpy(buff,
-			    (char_u *)_("1 more file to edit.  Quit anyway?"),
-							 DIALOG_MSG_SIZE - 1);
-		else
-		    vim_snprintf((char *)buff, DIALOG_MSG_SIZE,
-			      _("%d more files to edit.  Quit anyway?"), n);
+		vim_snprintf((char *)buff, DIALOG_MSG_SIZE,
+			NGETTEXT("%d more file to edit.  Quit anyway?",
+			    "%d more files to edit.  Quit anyway?", n), n);
 		if (vim_dialog_yesno(VIM_QUESTION, NULL, buff, 1) == VIM_YES)
 		    return OK;
 		return FAIL;
 	    }
 #endif
-	    if (n == 1)
-		EMSG(_("E173: 1 more file to edit"));
-	    else
-		EMSGN(_("E173: %ld more files to edit"), n);
+	    EMSGN(NGETTEXT("E173: %ld more file to edit",
+			"E173: %ld more files to edit", n), n);
 	    quitmore = 2;	    /* next try to quit is allowed */
 	}
 	return FAIL;