button: Allow :hover on insensitive buttons
button: Allow :hover on insensitive buttons

You can still hover a mouse on insensitive elements; it's up to the
theme to disable that.
This is in line with the HTML/CSS interpretation of :hover.

Insensitive elements still cannot be clicked.

https://bugzilla.gnome.org/show_bug.cgi?id=719486

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