Add index for 1.6 symbols
<title>Index of new symbols in 1.4</title>
<xi:include href="xml/api-index-1.4.xml"><xi:fallback /></xi:include>
</index>
+ <index role="1.6">
+ <title>Index of new symbols in 1.6</title>
+ <xi:include href="xml/api-index-1.6.xml"><xi:fallback /></xi:include>
+ </index>
<xi:include href="xml/annotation-glossary.xml"><xi:fallback /></xi:include>
</book>
