Use varyings for masks instead of overloading gl_TexCoord.

glsl/shp.vert

@@ -1,6 +1,9 @@
 uniform vec2 Scroll;
 uniform vec2 r1,r2;		// matrix elements
 
+varying vec4 TexCoord;
+varying vec4 ChannelMask;
+
 vec4 DecodeChannelMask( float x )
 {
 	if (x > 0.0)
@@ -13,6 +16,6 @@ void main()
 {
 	vec2 p = (gl_Vertex.xy - Scroll.xy)*r1 + r2;
 	gl_Position = vec4(p.x,p.y,0,1);
-	gl_TexCoord[0] = gl_MultiTexCoord0;
-	gl_TexCoord[1] = DecodeChannelMask(gl_MultiTexCoord0.w);
+	TexCoord = gl_MultiTexCoord0;
+	ChannelMask = DecodeChannelMask(gl_MultiTexCoord0.w);
 }