regex post submission patches/tidy up.

[SVN r7854]

introduction.htm

@@ -205,6 +205,13 @@ packages, and to a more limited extent perl 5. </p>
 <h3><a name="Installation"></a><i>Installation and Configuration
 Options</i> </h3>
 
+<p><em>[ </em><em><strong>Important</strong></em><em>: If you are
+upgrading from version 2.x of this library then you will find a
+number of changes to the documented header names and library
+interfaces, existing code should still compile unchanged however
+- see </em><a href="appendix.htm#upgrade"><em>Note for Upgraders</em></a><em>.
+]</em></p>
+
 <p>When you extract the library from its zip file, you must
 preserve its internal directory structure (for example by using
 the -d option when extracting). If you didn't do that when
@@ -414,3 +421,4 @@ with your message. <br>
 John Maddock</i></a><i> 1998-2000 all rights reserved.</i> </p>
 </body>
 </html>
+