Add an index for the table of syntax classes.

* doc/lispref/syntax.texi (Syntax Class Table): Add an index for syntax class table.

doc/lispref/ChangeLog

+2013-10-02  Xue Fuqiao  <xfq.free@gmail.com>
+
+	* syntax.texi (Syntax Class Table): Add an index for syntax class table.
+
 2013-09-29  Xue Fuqiao  <xfq.free@gmail.com>
 
 	* searching.texi (Regexp Search): Refine.

doc/lispref/searching.texi

@@ -1770,6 +1770,7 @@ Do not take action for this question---in other words, ``no''.
 Answer this question ``no'', and give up on the entire series of
 questions, assuming that the answers will be ``no''.
 
+@c FIXME: Document ‘unread-comment-events’?  --xfq
 @item exit-prefix
 Like @code{exit}, but add the key that was pressed to
 @code{unread-comment-events}.

doc/lispref/syntax.texi

@@ -141,6 +141,7 @@ Internals}.
 
 @node Syntax Class Table
 @subsection Table of Syntax Classes
+@cindex syntax class table
 
   Here is a table of syntax classes, the characters that designate
 them, their meanings, and examples of their use.