Broken/missing handler for taxonomy_term when class_exists is case sensitive

Normally http://php.net/manual/en/function.class-exists.php is case insensitive. However, there are situations where it can be case sensitive (e.g. http://stackoverflow.com/questions/15488632/php-class-exists-acting-case...).

I was 'lucky' enough to be in this situation. This caused to ctools plugin handler to not find the class LinkitPluginTaxonomy_Term because it looks for LinkitPluginTaxonomy_term.

I do not know enough about system administration to find out why, but this problem could be avoided by casing the classes correctly. In this case:

1. LinkitPluginTaxonomy_Term -> LinkitPluginTaxonomy_term
2. LinkitSearchPluginTaxonomy_Term -> LinkitSearchPluginTaxonomy_term

Hope this helps someone!