Bring back our own XML catalogs

Avoid 429 errors from W3C
diff --git a/lib/dtds/xhtml11/VERSION b/lib/dtds/xhtml11/VERSION
new file mode 100644
index 0000000..9459d4b
--- /dev/null
+++ b/lib/dtds/xhtml11/VERSION
@@ -0,0 +1 @@
+1.1