Make wxUSE_TIPWINDOW dependent on wxUSE_POPUPWIN

It doesn't seem to make sense to provide wxFrame-based implementation of
wxTipWindow, if anything we should use similar code to implement
wxPopupTransientWindow itself on the platforms not providing it.

So simplify wxTipWindow code by leaving only a single implementation,
using wxPopupTransientWindow. This should have arguably been done back
in 8962e1d938 (wxTipWindow is now a wxPopupTransientWindow instead of a
wxFrame., 2001-11-30) which introduced the use of wxPopupTransientWindow
in this code.

include/wx/chkconf.h

@@ -2414,6 +2414,17 @@
 #   endif
 #endif /* wxUSE_PROPGRID */
 
+#if wxUSE_TIPWINDOW
+#   if !wxUSE_POPUPWIN
+#       ifdef wxABORT_ON_CONFIG_ERROR
+#           error "wxTipWindow requires wxUSE_POPUPWIN"
+#       else
+#           undef wxUSE_POPUPWIN
+#           define wxUSE_POPUPWIN 1
+#       endif
+#   endif
+#endif /* wxUSE_TIPWINDOW */
+
 #endif /* wxUSE_GUI */
 
 #endif /* _WX_CHKCONF_H_ */