Update width and height

Property definitions

gamnit :: gamnit_android $ GamnitDisplay :: update_size
	# Update `width` and `height`
	private fun update_size
	do
		var context = app.native_activity
		self.width = context.window_width
		self.height = context.window_height
	end
lib/gamnit/gamnit_android.nit:283,2--289,4