This partially reverts commit 3c68696 (Make wxTopLevelWindow::SetSizeHints()
work in wxQt) because it breaks some wxSizer tests. and more importantly, it
breaks the documented behaviour of SetMinSize() which says:
Notice that calling this method doesn't prevent the program from making the
window explicitly smaller than the specified size by calling SetSize(), it just
ensures that it won't become smaller than this size during the automatic layout.
ee2dba802c