Xwt.Gtk.CairoContextBackendHandler: ensure that linelen <  text.length
Xwt.Gtk: implementation of MultiLine-TextEntryBackend
Limaki.View.XwtBackend.TextOkCancelBoxBackend: refactor to VidgetBackend<>
DragDrop: better handling of HtmlContent and priorities
Limaki.View.XwtBackend.VisualsTextEditAction: better size handling if empty text
hint: see GeckoWebBrowser.Gtk for Gtk-Binding of Winform