Ensure that the overall table border doesn't get overdrawn by cell borders with a different colour

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74830 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
patched for ICC

Signed-off-by: Marian 'VooDooMan' Meravy <vdm113@gmail.com>