Add a trivial virtual dtor to suppress g++ warnings.

Add a useless but virtual dtor to ValidationTraverserBase private class to
avoid g++ warnings.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73886 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Work around harmless g++ warning about possible uninitialized variable.

Return from the function before using the variables in the (impossible) case
they are actually not initialized.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73887 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Use WXUNUSED() to suppress unused parameter warnings.

Just suppress a harmless warning in wxCarbon build.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73888 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775