added backward compatibility for wp 3.0.1

git-svn-id: https://plugins.svn.wordpress.org/the-holiday-calendar/trunk@1035668 b8457f37-d9ea-0310-8a92-e5e31aec5664
minor fixes and validation

git-svn-id: https://plugins.svn.wordpress.org/the-holiday-calendar/trunk@1035669 b8457f37-d9ea-0310-8a92-e5e31aec5664