Normally, a set of classes like the ones in this directory would be placed into a namespace, such as `tt`. However, the names of these classes are designed to make it clear what class they inherit from, and if they were in a `tt` namespace instead of the `tt_` prefix, then adding `using namespace tt` would break the `tt_wxString` class and if it was also used with `using namespace std` then `string` could refer to either the tt or std version. Using the `tt_` prefix avoids that potential problem.
