Fix documentation bug about '\z' string escape.

doc/extensions.html

@@ -244,7 +244,7 @@ enabled:
 </p>
 <ul>
 <li><tt>goto</tt> and <tt>::labels::</tt>.</li>
-<li>Hex escapes <tt>'\x3F'</tt> and <tt>'\*'</tt> escape in strings.</li>
+<li>Hex escapes <tt>'\x3F'</tt> and <tt>'\z'</tt> escape in strings.</li>
 <li><tt>load(string|reader [, chunkname [,mode [,env]]])</tt>.</li>
 <li><tt>loadstring()</tt> is an alias for <tt>load()</tt>.</li>
 <li><tt>loadfile(filename [,mode [,env]])</tt>.</li>