Add a stylesheet addition to center the contents of div.titlepage.

This looks better (IMHO) for this article, but it looks worse for some
of the others.

en_US.ISO8859-1/articles/releng/extra.css

@@ -0,0 +1,16 @@
+/*
+ * Netscape 4 does not recognize the @import directive of CSS, so we
+ * can't add an additional stylesheet layer on top of the default one.
+ * Instead, we use this hack to copy this file to the end of
+ * docbook.css. 
+ *
+ * $FreeBSD$
+ */
+
+/* @import "docbook.css"; */
+
+/* Customization that looks good for this particular article. */
+
+DIV.TITLEPAGE {
+	text-align: center;
+}