GtkRange: Check "inverted" property when drawing

GtkRange: Check "inverted" property when drawing

The direction in which the slider moves can be inverted by setting the
inverted property. But the draw method does not check this, instead it
checks if the direction of the widget is set to be right to left.

Call the should_invert function in order to determine if the direction
of the range should be inverted. It too checks the widget's direction,
but also checks the "inverted" property, and allows the range to be
drawn inverted even if it is vertically oriented.

https://bugzilla.gnome.org/show_bug.cgi?id=746712