Fix handling of controls in vertical toolbars in wxMSW.

Not adding the controls to vertical toolbar is not enough, we also need to
hide them to prevent them from being shown as independent floating windows.
And we also need to add separators instead of the controls themselves to keep
the indices the same as in the horizontal case.

Closes #11821.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76098 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775