Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=55383
Improve markup for examples (part 1).

r1524838 broke the history of the WebSocket Example HTML files. This is because my patch file didn't contain the info that the XHTML files were copied from the HTML files (maybe this is not possible in a patch file).

This commit should restore the history of the files while applying the same changes and renaming them to .xhtml.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1526510 13f79535-47bb-0310-9956-ffa450edef68