Space was reserved for the borders even when it wasn't filled, resulting in
visual artefacts. Fix this by virtualizing the function returning the
additional space needed for the borders and only overriding it to return non
zero in wxAuiGtkTabArt.
Closes#14710.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72720 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Let wxAuiNotebook render the border itself, instead of doing it in dock art
class. This allows the notebook to do it correctly for the current theme.
Closes#14710.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72641 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775