Shift slot number to slot behavior mapping by six slots in H40 mode. This makes the line change slot align with the point at which the display turns on and off at the end of the active display area. Also fixed a regression in which an external slot got accidentally changed into a sprite draw slot

#version 110

uniform sampler2D textures[2];

varying vec2 texcoord;

void main()
{
	gl_FragColor = mix(
		texture2D(textures[0], texcoord),
		texture2D(textures[1], vec2(texcoord.x, texcoord.y - 1.0/512.0)),
		sin((texcoord.y * 512.0 - 0.75) * 3.14159265359) / 2.0 + 0.5
	);
}