[gtk+] Add an index for new api to the docs

[Matthias Clasen <matthiasc src gnome org>]

commit ca41bb440d0941d7553c552e83c9472299cd6a91
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Mar 22 02:11:03 2015 -0400

    Add an index for new api to the docs

 docs/reference/gtk/gtk-docs.sgml |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/gtk/gtk-docs.sgml b/docs/reference/gtk/gtk-docs.sgml
index 67c661f..dd5dd7f 100644
--- a/docs/reference/gtk/gtk-docs.sgml
+++ b/docs/reference/gtk/gtk-docs.sgml
@@ -467,6 +467,10 @@
     <title>Index of new symbols in 3.16</title>
     <xi:include href="xml/api-index-3.16.xml"><xi:fallback /></xi:include>
   </index>
+  <index id="api-index-3-18" role="3.18">
+    <title>Index of new symbols in 3.18</title>
+    <xi:include href="xml/api-index-3.18.xml"><xi:fallback /></xi:include>
+  </index>
 
   <xi:include href="xml/annotation-glossary.xml"><xi:fallback /></xi:include>