Add Windows 10 support to wxGetOsDescription(). Map Windows 10 to wxWinVersion_8 in wxGetWinVersion() to not change ABI.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@78285 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775