Fix issue with (?!) not being a valid expression. Update tests and docs to match.

[SVN r77602]

doc/html/index.html

@@ -198,7 +198,7 @@
   </p>
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
-<td align="left"><p><small>Last revised: December 24, 2011 at 18:02:12 GMT</small></p></td>
+<td align="left"><p><small>Last revised: March 28, 2012 at 11:56:40 GMT</small></p></td>
 <td align="right"><div class="copyright-footer"></div></td>
 </tr></table>
 <hr>