gtkfilechooserbutton: Align the label to the left
gtkfilechooserbutton: Align the label to the left

Using GtkLabel's xalign property so the label doesn't jump around when
the button gets resized.

https://bugzilla.gnome.org/show_bug.cgi?id=750477

chergert/gtk,alexlarsson/gtk,grubersjoe/adwaita,jigpu/gtk,grubersjoe/adwaita,alexlarsson/gtk,davidgumberg/gtk,Adamovskiy/gtk,chergert/gtk,davidgumberg/gtk,grubersjoe/adwaita,davidgumberg/gtk,alexlarsson/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,chergert/gtk,grubersjoe/adwaita,Adamovskiy/gtk,davidgumberg/gtk,Adamovskiy/gtk,jadahl/gtk,jadahl/gtk,grubersjoe/adwaita,jigpu/gtk,davidgumberg/gtk,Adamovskiy/gtk,chergert/gtk,jigpu/gtk,davidgumberg/gtk,alexlarsson/gtk,jigpu/gtk,alexlarsson/gtk,jigpu/gtk,alexlarsson/gtk,grubersjoe/adwaita,jadahl/gtk,Adamovskiy/gtk,Adamovskiy/gtk,chergert/gtk,alexlarsson/gtk,grubersjoe/adwaita,jadahl/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jadahl/gtk,jigpu/gtk,alexlarsson/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,jadahl/gtk,jigpu/gtk,chergert/gtk,Adamovskiy/gtk,jigpu/gtk