Support frameless taskbarless dialogs in wxQt

 * Moved frameless hint to window, checking border
 * Removed duplicate code in wxFrame and asserts that were preventing AUI to work

Thanks to @seandepagnier for the original patch

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77982 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775