This basically removes the "adv" library, even though it's still
preserved for compatibility with user make/project files referring to
it.
It is done because the distinction between "adv" and "core" was never
really clear (e.g. why wxTreeCtrl was in core but wxTreeListCtrl in
adv?) and it prevented some core classes from using adv ones.
Surprisingly, the wrong path somehow worked all this time and still works in
some installation, but not all of them. Using the correct path shouldn't hurt
though.
Closes#15570.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74979 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
