More themeable tabwin

Submitted by Peter de Ridder

Assigned to Olivier Fourdan @olivier

Created attachment 4020 TabwinWidget object and border-width, icon-size styles

Adding support for theming the color border and icon size of the tabwin. To support this the TabwinWidget needs to be a GtkWidget.

The attached patch makes TabwinWidget into a GtkWindow subtype. It doesn't use G_DEFINE_OBJECT to be less intrusive patch.

The patch includes border-width and icon-size style property.

Patch 4020, "TabwinWidget object and border-width, icon-size styles":
xfwm4.tabwin-object.2.patch