These classes can also be potentially used in the user code, as they are
used for the protected members of wxAuiTabContainer, so don't replace
them with just std::vector, but do, at least, use wxBaseArray template
for them instead of the macro-based object arrays.
Note that this required the check for the button presence in m_buttons
in wxAuiTabContainer::TabHitTest() as wxBaseArray::Index() relies on
object comparison, whereas the original version relied on object address
comparison, so keep it like this, even though we probably could compare
the buttons IDs instead (and, possibly, not compare anything at all but
just return the result of the button we found from ButtonHitTest()
directly).
Also document these container classes.
bceace12b5