Moved wxControl::GetBorderStyle into wxWindowMSW::GetBorderStyle
but added GetBorderStyle to have the same behaviour as before (so e.g.
notebook panels don't get borders)
Improved help window borders
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@47963 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775