GtkWidget: Fix clipping to large subwindows
GtkWidget: Fix clipping to large subwindows

_gtk_widget_draw_internal() was clipping by passing the subwindow
sizes as a path to cairo_clip(). This was breaking for windows
larger than 23 bits in width/height, due to cairo using fixed point
(24.8) for the path coordinates.

We fix this by pre-clipping the subwindow region to the existing
cairo clip region in the full 32bit gdkwindow precision. This fixes
the GooCanvas Large Items test.

https://bugzilla.gnome.org/show_bug.cgi?id=710958

jessevdk/gtk,jadahl/gtk,jadahl/gtk,alexlarsson/gtk,grubersjoe/adwaita,Sidnioulz/SandboxGtk,chergert/gtk,grubersjoe/adwaita,alexlarsson/gtk,Lyude/gtk-,jigpu/gtk,jigpu/gtk,jigpu/gtk,alexlarsson/gtk,Lyude/gtk-,jadahl/gtk,Sidnioulz/SandboxGtk,Lyude/gtk-,jessevdk/gtk,grubersjoe/adwaita,jadahl/gtk,davidgumberg/gtk,Adamovskiy/gtk,ahodesuka/gtk,jadahl/gtk,Adamovskiy/gtk,davidgumberg/gtk,jigpu/gtk,Sidnioulz/SandboxGtk,jessevdk/gtk,jigpu/gtk,Lyude/gtk-,Sidnioulz/SandboxGtk,Adamovskiy/gtk,chergert/gtk,Adamovskiy/gtk,grubersjoe/adwaita,msteinert/gtk,chergert/gtk,chergert/gtk,Lyude/gtk-,chergert/gtk,alexlarsson/gtk,alexlarsson/gtk,msteinert/gtk,chergert/gtk,msteinert/gtk,ahodesuka/gtk,msteinert/gtk,ahodesuka/gtk,ahodesuka/gtk,grubersjoe/adwaita,ahodesuka/gtk,chergert/gtk,msteinert/gtk,ahodesuka/gtk,jadahl/gtk,davidgumberg/gtk,alexlarsson/gtk,jigpu/gtk,Lyude/gtk-,jessevdk/gtk,davidgumberg/gtk,ahodesuka/gtk,alexlarsson/gtk,Lyude/gtk-,Adamovskiy/gtk,grubersjoe/adwaita,chergert/gtk,davidgumberg/gtk,alexlarsson/gtk,ahodesuka/gtk,Sidnioulz/SandboxGtk,Sidnioulz/SandboxGtk,davidgumberg/gtk,jigpu/gtk,msteinert/gtk,davidgumberg/gtk,grubersjoe/adwaita,jadahl/gtk,jadahl/gtk,grubersjoe/adwaita,jessevdk/gtk,jigpu/gtk,davidgumberg/gtk,jessevdk/gtk,Adamovskiy/gtk,Adamovskiy/gtk,Lyude/gtk-,Adamovskiy/gtk,jessevdk/gtk