inspector: Make it easier to cut'n'paste advice message
inspector: Make it easier to cut'n'paste advice message

The message says "Enable statistics with GOBJECT_DEBUG=instance-count"
but the message itself isn't selectable, making it hard to cut'n'paste.

https://bugzilla.gnome.org/show_bug.cgi?id=746391

jigpu/gtk,alexlarsson/gtk,jadahl/gtk,grubersjoe/adwaita,ahodesuka/gtk,davidgumberg/gtk,ahodesuka/gtk,jadahl/gtk,jigpu/gtk,jigpu/gtk,ahodesuka/gtk,Adamovskiy/gtk,Adamovskiy/gtk,chergert/gtk,Adamovskiy/gtk,jadahl/gtk,ahodesuka/gtk,davidgumberg/gtk,alexlarsson/gtk,Lyude/gtk-,davidgumberg/gtk,jigpu/gtk,Adamovskiy/gtk,grubersjoe/adwaita,davidgumberg/gtk,jigpu/gtk,Lyude/gtk-,jadahl/gtk,Adamovskiy/gtk,jadahl/gtk,davidgumberg/gtk,jigpu/gtk,grubersjoe/adwaita,grubersjoe/adwaita,chergert/gtk,alexlarsson/gtk,Adamovskiy/gtk,davidgumberg/gtk,chergert/gtk,chergert/gtk,grubersjoe/adwaita,jigpu/gtk,grubersjoe/adwaita,chergert/gtk,Lyude/gtk-,Lyude/gtk-,Lyude/gtk-,ahodesuka/gtk,alexlarsson/gtk,alexlarsson/gtk,alexlarsson/gtk,grubersjoe/adwaita,jadahl/gtk,Lyude/gtk-,Lyude/gtk-,jigpu/gtk,grubersjoe/adwaita,ahodesuka/gtk,alexlarsson/gtk,Adamovskiy/gtk,davidgumberg/gtk,chergert/gtk,ahodesuka/gtk,Lyude/gtk-,chergert/gtk,jadahl/gtk,Adamovskiy/gtk,chergert/gtk,davidgumberg/gtk,alexlarsson/gtk,jadahl/gtk,ahodesuka/gtk